It may have been of the TSA's work.
I had a similar problem just as the TSA was getting into high gear, delivering and setting up CTX machines en-mass, etc. I checked a bag, bag got lost, was delivered to me at home. I open the bag and discover something just isn't right - suitcase is mine, but the contents inside were not.
This was on another carrier and they paid the full claim. Thankfully I had receipts for most items as they were new - plus I had been shopping on this trip and some of what was in my suitcase was newly purchased in my travels (Nordstroms, Abercrombie & Fitch, stuff from REI, etc).
The new contents were more or less a teenagers clothing
, south park t-shirts and some other interesting things.
When talking with the air carrier, they suspected it was the doing of the TSA during a checked luggage search. I suspect they emptied two suitcases and put the items back into the wrong one. I never did get my belongings back - the airline wasn't interested in the 'gifts' I got, so I just donated the clothing to goodwill.
This was just prior to when the airline would blame the TSA and the TSA would blame the airline. Luggage was locked too.
I've heard of this happening to a couple of other people and read one account in a newspaper about it. Ain't the TSA great?
SDF_Traveler