I had a similar thing a few years back. Left my mobile phone on my seat, had already passed various gates and checkpoints and they did exactly the same thing. Within ten minutes I was re-united with my phone. I couldn't thank them enough.
Left my keys on the plane seat, and remembered once I was at baggage claim. All Delta would do is let me fill out some paperwork. I ended up having to have a locksmith come out to the airport parking lot to make a new key for my truck.
