In reply to andyd1970:
I used to work in a huge distribution centre for DVDs, they also had the contract for Morrissons DVDs and Games returns. This sort of thing was very common, customers would buy expensive games and films, take out the disc and replace with something else then take it back to the shop for a refund. The products came back to us where they would go through the returns process where they should have been checked but more often that not were just rewrapped, re-stickered and put back into general stock, which means that the wrong discs were sent out over and over again until someone physically checked. Unfortunately it was just not possible to 100% check everything due to the huge volumes going through every day. It was very hard for anybody within the warehouse to switch discs and get away with it, and I cant see any other facilities having less security that we had on site.