I think it's really lame that he told you it was a 'guy thing' and other girls showed up.
HOWEVER, I have been in situations where my bf brought me to things that were supposed to be guy's only, and his friends were pretty annoyed for bringing me, but they made the best of it. There's always one or two guys in the group that cave to their demanding females' demands.....or just want them with them everywhere.
If my man was going to Vegas with the boys, I wouldn't WANT to go, because I know it would be an intrusion. Don't assume the girls' company was entirely welcome.
Live as if you were to die tomorrow. Learn as if you were to live forever. - Mohandas Gandhi