Thankfully the only thing we have ever lost was an autograph book.
It was on our honeymoon, and we had been carrying it around for days. All the characters had written notes of congratulations in it. And somewhere near the end we lost it. It was not really a big deal since it was just a book, but I was a little bummed since it had all the congratulations in it.
We stopped by guest service & asked about lost & found. The CM took some information including our address.
We finished out our trip. About a week after we were home, an autograph book arrived in the mail with every page filled with notes of congratulations to us on our wedding from different characters, and a note from Mickey saying he heard about us losing our book & wanted to make it up to us.
It was so sweet.
11 years later, it is in our wedding box, and my DS loves looking through it.