I have left my wallet, my Blackberry, my wallet, my I-Pod and my wallet on planes (yeah, I should never put my wallet in the seat back in front of me...) and have 100% success getting the stuff back. The trick is not going through the DL process, but physically go to the airport and ask them to ask the people who were working at the gate when the plane landed. Even if the cleaning crew found the item, IME, they would have asked the ground crew if anyone reported losing the item.

Several years ago, I left my cell phone on a plane and went through the lost and found department. The next day, I was flying out, so I stopped by the Atlanta Room to see if it had turned up. I was told it hadn't, but dialed the number when standing here and could hear it ring. The DL employee at first wouldn't even check the ringing phone, until I pointed out that it was very unlikely that someone lost a phone that was sitting back there is ABBA's Waterloo as the ringtone. That made me realize the lost and found process is useless.