Theft in luggage is a huge problem. The TSA agents and the baggage handlers are usually paid very little and therefore there is a great reward for them to steal. I hope you take the case up the chain of command. Next time, pack ALL valuables in your carry on, in place of less valuable items like clothing or blankets. Keep a close watch and if you think a valuable item wont fit in your carry on, then dont bring it.
Theft in luggage is a huge