I messed up and he won't call me again.

Well, since your relationship with each other appears to be mostly online, send a friend request. It is the netiquittely correct way of saying "sorry" after blaming someone.

He may still care, and he may not be mad. Often times, when the communication is all online, it can get intimidating to try communicating with someone who has blamed you in the past. He may have simply given up hope. This is not entirely bad, by even sending a friend request, you open up a slight source of dialog.

The thing is, message him, and apologize, and see what happens. After you blame him, he has no initiative to try to restart communication.

I don't know how ur relationship with this guy is but I would say maybe you need to leave a message explaining that you want to talk. If he's sincere and mature about it, then he'll call back, if not, then I wouldn't waste my time

Well, actually, guys may be slow, but they're not stupid. You sent a pretty clear "don't want to talk to you" vibe. So I think you'll have to open contact again.