I was just guessing that you were clocked because like you said, why would they engage you then laugh and not keep up talking to you? It seems they were just getting their fun.
Some people, myself included, are very attuned to mannerisms, physical structures, a gender's common gait, etc., and can clock even the most unclockable. Maybe one of them is attuned to the differences...? Or, I am full of crap. lol