I do have sympathy. If someone stole from you, I bet you would be steaming mad, especially if it was something valuable.
They traded, she gave him the weapon, I don't think he gave her anything in return, accepted trade, and then logged off promptly. There goes a something good, and he didn't say anything I believe. No thank you, no please can I see the weapon. And when the other person asked for it, he logged off and cannot be tracked.
Why don't you post about it if you got stolen that way, eh? Got a really cool something and someone robbed you of it right underneath your nose, and you can't even ask for it back because they logged off and probably left you in the middle of mobs?