Thankfully, I have not experienced any of the disappearing furniture. Do either of you have Eco Living installed? If so, I've learned (I don't have this EP, myself) others have mentioned this is due to the "Sharing is Caring" NAP.
If you don't have this EP, I would consider doing one or both of the following things: Repair your game via Origin and see if that fixes it. If not, then do a folder refresh. If that fixes the problem, then you can trade out the new saves folder for your existing one, so that you have the same games to continue. If the problem returns, it's entirely possible your game save is corrupted. Best of luck
A thought that just occurred to me, is you could also start a brand new game save to see if this problem continues, then do the steps above.
Hope this helps.