I remember when the game first came out. I wanted to have a collection of gnomes. So I had my sim display the gnomes that he got back from the gem cutters. When I started up the game the next day, the 2 gnomes were not on the display stand. I figured my game was glitched. Now this was before CC or mods. So it was EA's standard reply to uninstall and reinstall your game. So I did what they told me. After the 4th time, I noticed the gnome move. He got down from the display stand and moved over near my sim's bed.
That is how I discovered that they moved. Oh gosh, all that time wasted by uninstalling and reinstalling the game!