IF it happens, saying “hi” is a good start.  After that just forget it.  

Get on with having a good time - they will!

Most guys who come to Menfriends are quite happy to keep
their being there private and respect that everyone else likes it that way too.
Chances are good that he wont want you saying anything either. 

We all tend to operate by the
principle “what happens here, stays here”