I have done it TWICE in this last week. I am a good looter even in FFA but I looted paldrones from SM by accident. We went through again and got them for the priest. I felt bad but ya get over it.
Later in Uldaman I looted a 2h hammer by accident. A pally could have used it but I was checking the loot out and pressed the button on the hammer when I wanted the mageweave. LOL It was AH bait for me but the pally needed it. I just said sorry but they keep crying about it and said I should give him some money for it. I said fek that, he can duel me for the money if he wants but I would beat him LOL!
Anyway admit your ninja looting mistakes for all to see.