My advice is to let it go, plain and simple.
But I do know how the OP feels as he's totally taking it personally. I once flew for a job interview arranged by a headhunter--he was to pay for the whole trip, but he only fronted the hotel, I had paid the airfare and rental car.
Up until the interview (this was like 1999) I was the 30 thousand dollar man to him. I remember he told me to make sure when they were going to make a decision and what was the next step. It was August, I asked as the headhunter said, and the interviewer said we'll probably make our decision in Jan. or Feb.
When the headhunter heard that, I was no longer a $30k commission for him, I was the $0 man. One month later, still no reimbursement for the flight, car, and per diem. I called him and told him I'm holding him to reimbursement as promised, and he was a co*** moth** f*****. I'm sure at that point I felt exactly like the OP. He told me you'll get your money so relax. Here's my boss' email, feel free to light a fire under his a** if you want. I did, and got my money. But like I said, I was young, it was 1999, and today, I'd let it go.