About 30 years ago, I was house-sitting for some friends for a week, and feeding their cat. During the week, my pocket knife went missing, and I spent most of the day looking for it. I found all sorts of things down the back of the sofa, including two full sets of car and house keys the owners had replaced long ago. By around 4.00pm, I had looked everywhere I could think to look, I knew where I had left my knife the night before, but it wasn't there. Looking out of the window, I saw the cat wriggling about on the grass, in a rather strange way, and wondered what it was doing. When I went to look, it was trying to get my knife off a magnet attached to its collar, which was used for opening the cat-flap!
The cat must have had it there for a whole day, and I was amazed that I managed to get the knife back, and that it didn't go to the Planet Biro, where all the lost things go