One, going to his workplace would most definitely ***be*** stalking. Two, he's roomie1's boyfriend, it's her problem to deal with now. You don't even know why he left or apparently why he dissappeared all those other times. Someone who pops in and out like that sounds like a flake who would be more trouble than they're worth no matter how much you like them. Why do all of you like him anyhow? Reading it again the situation is like a harem anime.
>Why should it matter that I'm a girl? There are other people keeping some form of an identity here.
It doesn't matter that you're a girl. What matters is that by using a name when you started the thread your post will naturally be coloured by every previous comment or advice you have given under that name. This is exactly what anonymous posting is good for avoiding, so you can get opinions on your ideas or problems without people attacking a built-up persona. Just because other people keep some form of identity doesn't mean it's beneficial or desirable for all occasions.