Staying in a hotel that requires a key to access the elevator. Lobby is smallish and could potentially bump into a co-worker while in the lobby. Looking for a discreet manor in which to pass off my room key to my lovely visitor. Considering going to the lobby upon her arrival and having her follow me up, but interested in other suggestions. Thank you in advance.

Older posts sometimes are "No Longer Available" so I will cut and paste some from 8 years ago. See the entire threads for additional suggestions.  
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http://www.theeroticreview.com/discussion-boards/new-york-2/fishing-for-a-solution-to-the-key-card-problem-257083
Fishing for a solution to the key card problem

Leave a key in a secured place where she can nonchalantly grab it.  
I've used plants outside or under the computer keyboard in the business center.  

I tell them what I will be wearing if they have not met me before,  or tell them exactly what chair I'll be sitting in.

When you’re spending time with friends knowing their names helps. I love overnights & vacays! Giving my full legal name is needed sometimes to make arrangements. If you want to leave her a key at the front desk this is the best way. You can always meet her in the lobby.  

Last I checked, providers are rarely sharing their real name. To get the key from the front desk based off the reservation, most likely she will be asked for ID. Is carrying a fake ID with your escort name a thing?

with or without panties, reminds me of an incident with a quite demented girl I saw in the Boston area. I got to her building and was waiting for her to buzzer me in to her front door. All of a sudden I hear her yelling to me. I turn and look for her as she continues to yell. Finally, I spy her on her balcony about five floors up. She tosses me her keys and yells down instructions on how to use them.
Discreet, eh?
Fortunately, no one seemed to be watching.
What a nut. Right, fish?

Here’s your chance to make this situation very erotic,
A post I did years ago and it’s thread about hotel security and bringing someone to your room.
Check it out

I told the client what I’m wearing and he tells me what he’s wearing. When I come in, we make brief eye contact, and he heads toward the elevator, with me following as though we are not together. And I just happen to get out on the same floor.

I met a companion once who told me the key card for her room was on top of her vehicle's left rear tire in the hotel garage. I thought that was pretty clever and we had a great meeting as well.

... my date comes down from her room and meets me in the lobby. Assuming the weather's decent, we take a walk around the block or two. We get back to the hotel and enter the elevator together. QED.

Winner! Read your story and that sounds like a great idea. Thank you.

1) tell her what you are wearing ..   ensure she dresses professional / discreetly ,,,, she can just follow you to the elevator  ..if you do casual and dont talk to her should be fine  
2) met in parking lot
3) i met one lady the night before in valet .. gave her my room key and number ..  idea was she was going to come in the AM and "wake me up"  

Most hotels requiring key card elevator access have floors other than the lobby that are accessible without a key card, such as the mezzanine or rooftop. I have met providers on these floors where there are far fewer people.  If it’s a provider, I have not met before I need to make sure they are whom they represent themselves to be. I have turned away providers that do not match their website photo /descriptions, and I would not want to do that at my hotel door.

Remember that when you're doing this, act like a boss. Skulking, nervous behavior, and elaborate schemes are more likely to draw attention from people who otherwise wouldn't notice you.

I prefer to meet outside the room (if the gent and environment are amenable) so daytime appointments usually entail me wearing a secretary/librarian look and meeting in the lobby bar area with my laptop. We greet each other as if we're colleagues, order a glass of wine and flirt quietly while appearing as if I'm going over some presentation. We settle up and keep an appropriate (if slightly fawning) vibe as we go up to my room to see samples of X product (fabric swatches, etc).
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Evening appointments have me dressed as if heading to a nice dinner and again meeting in the lounge. These scenes can play out as if we're already lovers or strangers picking each other up.  
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Since I only see 2 gents per day at the most, there's not a lot of 'traffic' to be concerned with. I've only had a few nosy bartenders but tipping generously and flirting with them has quelled any qualms (a woman has her needs after all😉).

I've done that. Actually, I entered the lobby from the street pretending to be talking on my cell phone. Once inside, I recognized her and hit "call" to call her pre-entered number. She answered, I IDed myself ("I see you in the blue dress. I'm the handsome fellow in the Armani suit, Rolex, ... and a rose pinned to my empty sleeve.") and made eye contact and/or a head nod. She hung up and I continued to have a fake conversation ("Sell as soon as it hits 123 and not a dollar sooner. ...") We converged without any sign of recognition as we both went to the elevator where she carded her floor and I just followed along. No problems. (Well, my fake stock transaction didn't work out as hoped but I broke even.)

Hence "if possible"

I do the same especially if I have seen them often. I usually like to see someone first at my place so I know who they are and if the vibe is great so if we decide to travel or spend an overnight at a hotel I can share my real name and they can leave a key for me at the desk and I have my ID to show when I get there. Simplicity is best.

...but every four star hotel i've stayed at always had some kind of bar or restaurant.  

This is exactly what the OP did not want to do. If this would occur in front of his colleagues it could raise suspicion.  Questions might be asked which then requires the OP to lie about knowing somebody in the city and never mentioning it before.  Among other scenarios.

yea, i can see this being a major problem with outcalls where there might be a sales convention or an office training with lots of familiar faces...i've gone to the latter quite a few times and when co-workers are about, having a hot woman meet you and go back to your room is going to look bad if they see it! there is also the risk of getting into trouble for misconduct as you are there on "official business" and the company is NOT paying for your room so you can host escorts!  

Plus, it might look somewhat suspicious if you were staying over several days and had a steady line of women who all are named either after some type of luxury automobile or adult beverage wanting to go up and see you.......

Solution that worked for us. I sat in the lobby on my laptop with a glass of wine. Not unusual at all for me. Kept the seat next to me "reserved" (apologies to the elderly gent who wanted to sit down). Had small talk with a colleague who sat in the seat for a few minutes. When the lady entered the lobby, we made eye contact; I vacated my chair leaving the room key underneath the small decorative pillow in the adjacent seat.

Similar to my experience. The lady I was seeing told me she had a vehicle parked in front of the hotel. Gave me the description and the plate and said the key was under the driver side windshield wiper.

This is interesting! I feel that most of us who are driving our personal vehicles to appointments wouldn’t want to  make a vehicle identifiable to clients for the future, out of concern for potential stalking. If it’s a rental car, sure, I could see that. Of course, being based in Chicago, our cars, wipers and tires are all often covered in snow…

I recall the hotel but since I've been there twice I'm not sure which girl it was. One was an agency girl, the other was indie, if that matters.

Every August I go to vegas for a big convention, so i have to be discreet during that time. So I tell the lady to follow me when she sees me, and be cool on the ride up. I snap a pic of myself so she knows what Im wearing.  

If a client cannot be seen with me due to colleagues or friends/family. I ask if he can meet me on a certain level of the parking garage and please provide description of himself and his attire.. Hand me his second key I wait a minute or two and walk far behind him. We do not speak until we are in his room and I had him his key back. I have been doing this for years with no issues. I live in a city that regularly has conventions.
Have fun!

Dont shit where you sleep or work.  

There are many reasons I like to have a video vibe check before our first date in person, but this is one of them: being able to recognize each other, for certain, makes logistics easy and also eases the nerves. How wonderful it is to meet someone for the first time when you already know exactly what they look like!