Hi Nichole, this must be so frustrating for you. I very much doubt that he's going to want to come back. And even if he did want to come back, you'd be crazy to accept him. He's shown you how thoughtless he can be - so do yourself a favour and don't let him back into your life. Frankly, I don't believe that he dropped his phone in the water either....it's just too convenient given his current behaviour.
As for what went wrong, we can only guess. But in order to guess, there's a bit more background we'd need:
1. how long had you been seeing him before this happened? Were you an official couple?
2. was the relationship happy or did it have 'ups and downs'?
3. if there were problems, what kind of problems were they?
I assume you still don't have your jacket. Do you have any mutual friends who could pick it up for you?
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.