Left a fairly nice watch on the nightstand at a Minneapolis hotel some years back. It wasn't my last day there, so I don't know what would have happened if I had left it and checked out, but it was there when I got back that evening. Given that the housekeeper couldn't possibly not have seen it and didn't take it, I suspect I would have gotten it back, though. (Wish I could remember what hotel it was to give them a shout-out here, but I don't. I worked for Honeywell at the time and it was during one of my non-infrequent trips to corporate HQ.)

Left two items on airplanes that I remember. One was a library book on a plane when I connected somewhere in the southwestern U.S. - PHX or DFW, doesn't matter. Got a call from AA that afternoon. Said I'd connect through some other airport on my return east a few days later. They had it waiting for me there. (I don't know if they would have done it for anyone, but I was Executive Platinum at the time and could have received special treatment.) The other was an iPod, back when iPods were cool, that my late wife left in a seat pocket in São Paulo when all the passengers who boarded in Rio had to disembark and re-board to leave Brazil. We returned to the same seat less than an hour later, but it was gone. Permanently. Also, not on an airplane, but I left a decently expensive digital camera on an airport bus in Iceland once. After looking all over for it, including going back to the same bus, I gave up and we went through security. It was waiting for us at the screening station. So - two for three, with the lost item being in the middle as regards value.