That's why you leave a deposit. You can't trust people these days, it really sucks.
That whole "mom" thing was nothing but an excuse. He reflected on the deal he had made with you and realized that he had f'd up about the head unit... so he did what he did. Don't worry about it man, from what it sounds like, you can find a better one somewhere else.
Good luck!
BTW, don't really know what this is doing in hybrid.....