If you saw him put them in his suitcase it sounds like the loss happened at the airport. When my DH's luggage is "inspected" by the TSA they always leave a flyer in the suitcase that says it was inspected. Was there anything like that in your son's suitcase? If so, there is a remote chance is fell and wasn't put back into the suitcase. Might be worth calling the airport and reporting it missing....I've read others say they've done this and been told there is a lost and found, but sadly I've not heard of anyone getting their stuff back.

But maybe you could be the first!