Are you kidding me? of course I have.. I used to run into them years ago.. and now EVERYWHERE lol.. These days they know me from the VH1 show, and usually come over and say hi to me.
Prior to that I would spot them because of them peacocking, or because I would see them running routines. Many times I would find myself in set with a couple of women, and another guy would join us.. part way through we would realise we were both in the game, and would subtly acknowledge it with a nod or comment. They were usually cool.
You could say, "hey you look familiar do you know my friend Neil Strauss?" or just use the secret handshake
If someone is cool then fine include them and chat to them.. If they have good game and you can learn something then take notice.. just don't make it obvious and weird them out.