What do you do, when you find out someone you've played with, is quite possibly in a relationship, but hasn't disclosed this to you?

The internet is a wonderful thing, and with a name, it's really easy to find a FB account, when you know where they live. This is how my bf found out, said person is, very possibly, in a relationship. His page says single. But they have pics together. Hers says relationship. And comments alude to them being "a power couple."

I personally like knowing that they are either;

A. Single
B. Taken, but allowed to play around(I just assume they are being honest with this one) C. Cheating (because then I don't play with them) When someone says discretion is a must, I seriously automatically assume cheating. Because obviously everyone is gunna be discreet about their hookups, but this right away, to me, says cheater.

I met someone last night, maybe it's my bad, I just assumed he was single. His profile didn't actually state this. But it also doesn't mention a partner.

I don't want to play around with married/taken men, if they are doing it being their partners back. I don't want to be a homewrecker.

I'm actually pretty upset right now. And because I'm such an emotional person, I'm trying my hardest not to cry over this.

First time meeting this guy, and he was actually really nice, genuine. I felt extremely comfortable with him right off the bat. Of course there were a few awkward pauses here n there. But that's normal, when meeting someone first time. But it was really nice, because I was like, oh this is awesome, I've found someone whom I can play around with, and it'll all work out.

To now feeling like I was lied too.