I was recently contacted by someone asking about a girl I reviewed. He asked if I saw her at a specific address and gave expicit location floorplan and room details. I didn't see her anywhere near that address. However, I am now concerned for her safety as well as anyone else this person may try to see from this site in the future. What is the best way to report the user and also let providers/agencies know about this person? My guess is he is either LE or a stalker, he has posted no reviews and only one ISO on the boards.

Use the "contact us" link at the bottom of each page.

Not much you can do to alert providers or agencies, but yes, at least report the suspicious contact to TER.

You can start by telling the provider you saw. Give her as much detail as you can. Then, if he does contact her and she gets more contact information, she can get it added to the secret escort balcklist.

There's no single blacklist, and some are not so secret.

To some girls it means landing on their "Do Not See List." A true blacklist is a site where guys who've mis-behaved have their information shared so girls can avoid them. And if you're on one, you probably don't even know it.

I told the provider and she has never been at that address before. She's not even the same ethnicity!

Thanks for the replies. I left one thing out of my initial post. The girl I saw was a different ethnicity than the one the stalker was trying to find and she said she had never been at that address before. The guy seemed unhinged. I already was going to report to TER but I didn't know how to alert the provider community.

There is certainly a more popular one. I didn’t say it was the only one though. And obviously the secret isn’t so secret. Many know about it but providers still guard it like we don’t. So I was being a bit sarcastic. If it was so secret, I wouldn’t know about it and be posting it here.

Be careful about volunteering information.  Your Interrogator wants info from You and may manipulate the discussion.
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I: Is this Mary a tall blond with a rose tattoo on her left shoulder, walks with a limp, has a French accent, ... drives an old red Citroen with AZ plates?
Y: No way! You have the wrong Mary. You are waaaaaay off base! THIS Mary is a short long haired brunette with blonde highlights, has a tattoo of her BF's initials on her ankle, no limp - fit as a gymnast, has a Jamaican accent because she is a black girl from Jamaica, but happens to live in Jamaica, Queens ... and she drives a fairly new blue Mazda with NY plates.  
I: Gee, I guess you're right. She is the wrong Mary. I am totally looking for someone else. I'm sorry I wasted your time. But thanks for your help. I can validate your parking for you.  
Y: No problem. Any time.  
Y leaves, but listens outside the door.
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I (talking on telephone): "Yeah, it's her. Alert the crew in Queens, NY!"  
Y: Uh oh. Did I say too much?

I've heard of mrnumber and verifyhim. Any others? Supposedly guys can't use the sites but how they would know?

Is being blacklisted that serious? What if the provider feel vindictive? Seems like a load of bull. I’ve  been scammed before and maybe blacklisted! Anyone can make up a lie and try to ruin your reputation!