It's happened to me on my nec.
Say someone kills you when you try and pick up your body. You're str bugged for whatever reason and dont have enough str to pick up everything.
You now have more then one body with items on it.
If you don't pick up every body before you leave the game, you get the body that has the most ingame gold worth.
It's happend to me before with items that I've had since I came off ladder- so it wasn't because it was unperm items.
Just douchebags nking you when you have str bug.