This happened three times.

I was in creative, and went to drop some items, my game freezes (lag spike) and then I accidentally dropped my sword. When I went to look for the sword it was gone. I even teleported all items to a hopper, and then looked in the chest and my sword was not there.

I have one clip of it.

Now watching the clip, the smooth stone was duplicated. It dropped the sword as if it were a smooth stone.