If you're telling the truth, you can go file a police report or lodge a formal complaint at the airport. There are surveillance cameras all over the airport (and in over 300 hotspots in the valley).

My cousin left his passport and a bottle of liquor on the trolley recently. Upon returning back to the airport, we had the cops take a look at surveillance cameras. An employee was caught taking the folder w/ documents and liquor. Since the incident had taken place the previous night, he had all the time in the world to return them; he didn't, though. The result? He ended up getting fired while my cousin got his goods.