I can't wait to hear about your solo trip! I leave Tuesday for my first solo trip in Disneyland. It is VERY short (Tues afternoon to Thurs afternoon) but I am so looking forward to doing what I want, when I want.
We also lost a backpack in WDW about 4 years ago; keys to the rental car, hotel safe, and various other important things. We were sitting on a bench and got up and walked off with it sitting there. Yay for amazing Disney security, who picked it up and returned it to Guest Services, and we were able to pick it up from there as we were leaving the park that night with EVERYTHING intact! We didn't know they had found it so we had to keep checking in every hour or so. Needless to say we got our steps in for the day in EPCOT that day!