I worked at Wal-Mart years ago and even then we had people who would buy something, come back, pick up something else, and then try to walk out without paying and using the old receipt.
He said they'd come in wearing rain coats and there'd be someone underneath the other guy's legs reaching up to snag CDs.
There's no end to what thieves will try.
One day I was looking at a printer on sale in a box down on the lowest shelf at a Wal-Mart. Looking back at me was a camera pickup! There are thieves who simply can't imagine that Wal-Mart has thought of their tricks.