Truer words haven't been spoken, and sometimes, like stated before by others, it is usually based on the most insignificant shit imaginable that make the event happen in the first place.

I have a few stories like this Julie too, that end with not all that much closure, and a boatload of wondering what the hell I did wrong to cause it in the first place. The best advice I can give is to keep trying, at least for a little bit anyway, and if he still doesn't response, or give you any incling as to what happened, then unfortunately, that is going to be the most closure that you're going to get.

It sucks, it hurts, but at least you know that it's over.