"Sunday morning rolls around and I'm unable to get a trailer". Maybe he took the day off work Sunday and you really screwed him? You shouldn't have promised to pick it up if you weren't sure you could. He did hold it multiple days and come all the way down to your price.
It wasn't your fault, but you made some mistakes. If someone comes down multiple hundred down to within $100 maybe give them a break?
Of course what he did was ten times more wrong.