I will say that you are not the only person who has experienced this issue, I have heard about this happening at least once before. A cause or solution was not found at that time.
I was wondering, did you leave the items in containers (chests, cabinets, end-tables), on the floor, upon surfaces, or inside display cases? Which home did this occur in?
Answering these questions may provide clues to the item disappearance, illuminate possible preventative measures to help safeguard a duplicate scenario among the community and possibly a way to troubleshoot/fix the issue.
Posting this in the Hardware and Software Issues Forum may be more beneficial to you. You may get a larger audience and concern toward your issue. Thank you.