A secret scammer? or hacker?

Yesterday, 11/27/11, my bud Darkbraken was scammed or hacked his Nonmember wings. This is what happened: A person traded Dark a collar for his Nonmember wings. Although, dark didn't even have them for trade! Then the trade said "You got a COLLAR!" dark didn't accept nor decline the trade. he thought maybe it was a glitch but he logged out then back on to see if they were there. Sadly enough, they weren't. Was this a scam or a hack? D: