Official comment
rekordbox keeps 3 backup copies of the database; every time you launch the software, it creates a new "live" copy and moves the previous version to the next backup. If you ever notice a problem or make an accidental deletion, it is possible to roll back to the last good copy... but if you've closed / opened rekordbox more than 3 times, you've lost your "good" copy.
Regarding relocation, you can mass-relocate, but again, without knowing the particulars of what you did to the music locations, it's hard to provide concise instructions on how to repair it.
