He sounds like a real jackass. It's still technically your money, even though you told him not to worry about it. Just throw some technicalities at him, and say, "I didn't necessarily say that I never wanted it, I just said don't worry about it, and it was a momentary thing. I need the money now, and I'd really appreciate it if you gave it to me." Also, have you ever smoked him out before? More than once, perhaps? If so, just tell him that you've been generous to him and have smoked him out many times. It's not his money anyway, it's YOURS. It doesn't give him a right to take part of the ticket money when he had nothing to do with paying for your ticket... what a fuckhead.

I don't agree that it was a gift that you cannot take back. He was not right to pocket part of the money IN THE FIRST PLACE.