Invalid ? (?)

Greatings !

I'm a player of Team Fortress 2, a casual one for saying..
I just play for fun, I don't even had a premium account for playing, but actually had some good items, after a long time trading.
But now lets skip to the bad part.. I was doying my regular trade on some servers, when this guy steamcommunity.com/id/Keron appeared, he said that was buying my items for 20 dollars ( I don't know if is illegal or not ) but at the same time, I accepted his offer, which f2p wont accept a money offer, searching for making him account premium right ?

And different for a great part of players, I'm not here for fight and make a war to bring my items back, I'm just here to take this guy out of Team Fortress 2, his nature its not a good one. I don't know if something will happen, I'm just wondering what can some people do, just for being better than others.

Here a following ss of my Inventory History :

Reporter resubmitted in proper format here: http://forums.steamrep.com/threads/76561197990564831-keron.8459/