As a guy who cart attends usually 2-3 times a week... there is no way in hell should anyone but her be held responsible for anything. We're not there to clean our parking lots, we're sent out with a vest and walkie and keys to start the QuikCart machine/operator they give us and that's all. We can put trash in the cart that's attached to the operator but that's usually trash you'd find in the carts themselves.
I have no idea where she found this needle but it was probably somewhere where cart attendants don't go to unless there's a cart there... usually the back of the parking lot or the far corners.