A Friendly Agreement

I just had a ranked game where there was a person, summoner name withheld for their privacy, and they said that could Vayne top and though it is viable in my ELO it is virtually unheard of. They said they would get first blood and I said no way in heck. And then I said I'll give you a skin if you get first blood but if anyone else does, you give me one, and i asked deal? And the Vayne said deal. Lo and behold, Vayne doesn't get first blood and then at the end of lobby, I asked for a skin, I asked for a mystery skin, which is only 475 RP which I believe to be more than reasonable but the Vayne said no and just skipped out of lobby and left and had't even offered anything. just straight up stiffed me. I mean I don't know if there is a way to force them to give me it but is there some kind of slap on the wrist or small punishment they can be given? I admit I'm a little salty but I feel that the summoner should be held to their word, I planned on following through with mine and Vayne, sadly didn't. Is there someway the Tribunal can say to this person, "Hey, don't be "That Guy" or else we'll put you in low priority queue?" Because I'm pretty sure that is considered scamming isn't it? Thanks, Jay Zenith