I'm writing because I was talking to someone on here and they're not who they said they were. Of course that's the chance you rake when you do online dating. This guy told me everything Iwanted to hear. Well we talked for about 4 months. So after a month I deleted account, thinking he did too. Not!!! So out of couriosity, I look on here, look up username, there he was, on here. So just be careful what you believe when they tell you all you want to hear.

If he gave you no clue you were going to be exclusive, there's no reason to expect he would deactivate his account. Then it's just your own expectations. This is where many people go wrong, I think mostly women, assuming you are in a relationship or exclusive etc. The best thing is to address this issue and talk about it, not assume.
Also, if he is still here, doesn't mean he's still actively looking / talking to other women.
So unless you know this for sure, you are again assuming.
And even if he is still active here, it might not be a lost cause. Maybe it is, not enough information to base an opinion on.
If you have real reason to know / think he's not for real, learn from it. Next time talk about these things and don't think/expect/assume you are in a relationship or both wanting to go exclusive too soon.

Hope you don't let it affect you too much, there are good guys out there!
Good luck