Is there any chance you could spoil it, and then blame it on someone else? Be like, "I know it says that was my username, but I swear to god it wasn't me." Or you could try the other classic technique, "It must have been those damn Martians! They're always doing stuff, giving away secrets, and scouring through my refridgerator! How else do you explain two pot roasts gone in one evening?!?!"
If they try to pin anything on you, just fight evidence with evade-ance.