You’d think that by now I would know better (this is hopefully helpful to newish mongers on the board)…

Looked over the talent of a local agency that I never used before and saw someone I liked. So, I contacted them via P411 (my default method). Shortly thereafter I got a reply saying “you are penciled in, contact us on the day”.

On that morning, I shot them a message (still via 411), confirming and asking for the details. Checked my message board a few hours later nothing. Checked again at T-45minutes and no reply. So I sent another message saying “I guess that we’re not on, so sad”.  

Fifteen minutes pass and they reply “sorry we missed your message, we don’t always check emails, text us at xxx-xxx-xxxx” (their phone number, on their P411 profile). I text and they tell me the lady is ready & waiting at abc hotel. Well, there is no way I can make there in reasonable time, so we cancel.

Though they admitted their mistake, I am irritated (missed opportunity) and the provider is now short some $$.

I could kick myself: after not getting a reply on the day-of, why-the-fuck did I not think of using the obvious alternate channel?

I would object and say "not good enough".

Either confirm me or I keep searching.

 
Time is the ultimate cost.   It's the only thing we have that we can't make more of.

Absolutely. You can never get your time wasted back. Sorry.

When they said to contact them on that day my immediate reply would be "how do you want me to contact you that day?"

 
Usually after contacting a lady on P411 we switch to email since logging into P411 to get messages can be a hassle. After that it's almost always texting on the day of the appointment (or day before) to get the location.

you learned that texting gets a reply from them a lot quicker than a P411 message.  I usually depend on email over texting and have also learned that some providers do not regularly check their email.  Apparently texting is better for many.

With ladies that I have an established relationship with it's almost always texting to make appointments and really all communication.  

 
With someone who is new to me I will ask what her preferred method of communication is after making initial contact.

and when they say something vague like "penciled in" or "I put your name on the schedule", I ask for immediate clarification in the form of a written confirmation.  You're right, anything less is not good enough.

require an email for FIRST contact, but once you have established yourself, they will have given you a phone number, and then texting is always my preferred method of asking for a subsequent appointment.  Most providers and bookers are not far from their phones, and they might let a phone call go to voice-mail, but they will usually look at a text right away, even if they are involved in doing something else.