Most Helpful Guy
I know what you mean, there was a girl at the gym who I met through some friends once and turns out she worked out at the same gym I did. I didn't even notice her but I saw some girl looking me weird. Usually girls don't look at me at all. So I got suspicious.
Then I realized I had seen her before. I didn't want to disturb her workout so I just went about my business. Later on she called me out on it and I felt bad.
Another thing is I don't want to chat up too many people because the more people you get friendly with at the gym the most you get disturbed from your workout because they come chat with you.
Just because I've met a girl before doesn't mean I'm going to go say hi or talk to her somewhere else. She might think I'm hitting on her or that I like her. Or maybe she thinks I'm a douche and will talk for a bit but really wishes I wouldn't interrupt her workout.
** So this guy should know it's OK to come and talk to you. how would he know unless you give him the right signals.