[Zubersoft]

No, you definitely do not want to use Import->Local File. That would reimport the files, and MobileSheets would assume you are trying to add new songs to your library. You just need to copy all of the files used by your library from D:\Gig Books to the LocalState folder, then use Settings->Other Settings->Fix Broken File Paths. It sounds like you didn't manually move the files from the LocalState folder to some other location, so I'm not sure why those files went missing in the first place, especially if you never changed the storage location. 

Mike