Left our kindle on a plane PDX-SFO en route to KOA earlier this year. Realized as we were walking out of the gate area for the arriving flight in SFO. Gate agent was too busy to go check herself (plane was on it's way somewhere else) and though asked the cleaning crew to check our seats it was surprisingly never found. She said that at SFO alone they get about 50 electronic items per day (phones, laptops, kindles etc).
We emailed lost and found etc and never got it back. I discovered later that it was de-registered from my Amazon account within *6 hours* of us leaving it (before we even landed at KOA).