Why didn't you ask him/her? It's not creepy to ask somebody's gender, especially when most of you guys aren't that pervy after all. Seriously most of you guys have been super nice and polite to me 
I thought of that. I decided it really was not important; since they are not really a dating prospect. I try to avoid mentioning my own gender.As you mention, women get dozens of PMs..which guys don't. I don't think it is fair to hound the few women that do make an appearance. Being mostly anti-social, I rarely PM people: male or female.
If I wanted to get serious about looking, I would try local activities that interest me first. As I understand it, long-distance relationships rarely work out.