Really??
You were conditional friends. More than likely the kind of friend that he was interested in seeing nude. As soon as he got his girlfriend back, the need for new friends was erased. I hate to put it so bluntly, but that just is what it is.
New friends happen to guys accidentally. Especially if they're attractive women. And more than likely, unless we're still trying to boink you, we're going to let you fade into the sunset once we find a more suitable partner. What would you all have to talk about anyway? His girlfriend? I'm guessing that's not what you wanted.
So point is, dude probably liked you to some degree. But upon reengaging with his ex, who he liked a lot - enough to commit to - he didn't really need or want to have any extras that he just met hanging around.
But go forth and connect with some new beau and make whoopy. Be free.
Float. You don't need a dude who isn't interested in you soul as much as your body.
Body & Soul. It's not just a soul series, its a mantra.
Even if he wasn't interested in you as more than a friend, he might just have cut ties to keep his ex from worrying or getting the wrong idea. Not saying it's right for guys to drop their platonic female friends for their girlfriends, but it happens.