Thread Drift Alert!
Not something of much value; but I left a book on a plane about 8 months ago. Realizing I had left the book after about 15 minutes, I went back to the gate. The door to the jetway was closed, but there was an agent at the desk finishing some paperwork. I told her of the problem and she unlocked the jetway door and let me on to the plane by myself! She stayed at her desk in the terminal .
Not being an airline employee, it was a kind of a weird experience to be on a plane by myself. I thought I was going to be assaulted by group of wand-waving TSA agents at any moment.