I had to travel recently, had a somewhat similar experience. I left my drivers license at TSA. Ever try to rent a car without a drivers license? Ain't happening, had to take a cab to the airport, and talk the desk clerk into renting me my room at the hotel. The airline called me and told me they had the license. My son picked it up and over-nighted it to me at the hotel.
I have never left anything at TSA. Near as I can figure it, TSA was hustling people through having their stuff X-rayed. Why, I don't know. The airport had a brand new spiffy microwave scanner and they were putting everyone through it. Just one scanner mind you, so the line was the longest I have ever seen it at out little (5 gates) airport. So I had to empty my pockets of everything into the gray plastic bin, even my boarding pass and loose license which I normally never let out of my sight - or possession. They're normally in my shirt pocket.
In this case, I think TSA was distracted - the guy grabbing the plastic bins was talking with another one and grabbed two of my bins - one of which had stuff still in it, my shirt pocket stuff. I said something and grabbed the papers and pens - and apparently missed the license. That ain't happening again!