If all merchandise in the Amazon Go store have been RFID tagged, this is a non-issue for checkout, as the turnstile tag scanner should be able to sense the items you take out of the store. As far as randomly put back at a different place of the items, the staff can use the tag scanner to detect that and fix it up even easier as oppose to physically locate the item by human vision which is arguably harder and less efficiently.

We don't know the details yet but RFID may solve this issue completely.