There was a spate of this at Luton Airport about 2 years ago. It had happened to me when travelling from Luton to here, I actually had a digital camera stolen which was hidden in a shoe right at the bottom of the case which led me to believe it was at Luton when the bag was scanned. I did quite a lot of 'investigating' at the time with the airline, the handling firm at Luton and the police, apparently there was a 'cartel' of thieves working in amongst the baggage handlers at Luton but the police just couldn't catch them at it. Incredible when you think how tight security is for us humble passengers! The other annoying thing was that my holiday insurance wouldn't pay out because, get this, the bag wasn't in my possession at the time!