When my kids were little, we had a little black ShihTzu named Ming Toy. She was a wonderful little dog, went with us everywhere, and was excellent with the kids.
Like happens in most families, we had lost socks, especially the lids would always be missing one or even both of their socks. We looked everywhere, with no luck. Even their knitted slippers would disappear.
One day, we had to move the living room couch for some reason. There, laying all over behind the couch, were all of the lost socks and slippers ! Ming Toy had been taking them secretly, and she was small enough to wiggle behind the couch and hide them.
She still would steal our socks, but at least then, we knew where to hunt for the lost footwear.