I have had this happen to me - twice.
First time, I was boarding an airplane at Pearson Airport. The MPA (not to be named) worked for the airline. I was travelling alone, and thought about saying hello (after all, I had a session with her about two weeks prior to my trip). But, I changed my mind... because these MPAs have stage names to protect their privacy (as we have one for massageplanet.net; cause my real name isn't Dealer). So, being in large airport, it was easy to slip into the crowd and avoid the encounter.
Second time, I wasn't as lucky. I was attending a bachelor party (so called "stag") at a hotel banquet hall in downtown Toronto. As soon as I walk into the place, the greeter/ hostess for the evening was a popular MPA. I was a bit stunned, but she wasn't at all. She treated me like I was her best friend. My buddies thought she was great. Never did I or she mentioned how we met. Nevertheless, we eventually talked at the end of the evening. I found out how much of a real person she was... house, bills, etc. I did go back for a session that next week. It was the best session I ever had with her. She is no longer a MPA... too bad.