As much as you may not want to admit it, perhaps this was just the ticket that he needed to get out of the relationship. Guys are wimps sometimes and can't just break up with you. They will wait until they see a window of opportunity to blame it on something you did rather than actually tell you they don't want to be together. So I am saying, maybe there was more to the break up than you seeing your ex one time
I hope everything turns out okay. Just try not to bombard him because then you will seem overly eager, and if he is treating you bad/ignoring you, you deserve better