To expand a little bit on above, what happened was (assuming Auto Import was on, because that is the only way it would happen):
1. You moved the files in Windows Explorer
2. Auto Import in MC found the moved files, because it detected file system activity, and imported them again. This can happen
very quickly on a local hard drive. On a NAS I would expect it to take a little while. So maybe not all files where re-imported before...
3. You ran the RM&CF function to point MC to the new location. But it was too late anyway. MC had already re-imported at least some of them.
If you only did this recently, or over a short period of time not long ago, you might be able to fix the issue by:
a. Backup your current library manually just in case you need to revert to it, if something goes wrong.
b. Restore a library backup from before you made the changes. MC makes backups automatically, so you should find one. Note that you will lose any and all changes made since that backup, not just these move changes. So you may have some work to redo if you have been doing some tagging.
c. Immediately turn off Auto Import by unchecking the setting at "Options > Library & Folders > Auto-Import > Run auto-import in background"
d. Use the RM&CF function to point MC to the new location of the files you moved.
e. Turn Auto Import back on when the above has finished and you are satisfied it worked.
As a side note, I believe that you can update the [Date Imported] field using the "Data Fiddler" component of the "
Swag of Tools" utilities. But if you wanted to do that, what dates would you set the field to for all your files? Restoring a library backup is the only way to get the original data back.