That is terrible and makes no sense, unless you have a cloud backup service like OneDrive coming in and restoring stuff to an earlier state…
If you are using OneDrive, it’s a longshot, but you might be able to use it’s File History to restore or revert changes that have been made to your Project Folder from this… but I have no experience here and not even sure it will restore it correctly, but I have my fingers crossed for you…
Before you do though, Check-in Changes now with URC and make a snapshot incase something goes wrong…
Make a snapshot of all your other maps too while your at it
It’s essential to Check in Changes and make a snapshot with URC, if not daily, at least everytime you make an update.