At a hotel the Mrs and I were staying at in Germany, the duvet for the double bed was slightly smaller that the actual surface of the bed itself (so no over hang). Meant when the two of us were in the bed, it would clearly not cover our bodies. We thought they'd put the wrong duvet on it (like a single or small double). We were told that was the correct size (???) and so we asked for an extra and so had one each for our 3 night stay.
So no stealing that way!
Really comfy bed and a nice hotel other than that!