Unless the drive is really cooked you should be ok. It often happens with my cheaper drives, I usually just open Disk Utility, the drive icon may be there but not highlighted (if they’re not there highlight on the main drive) you then just click repair permissions, I’ve trashed my FCP permissions which worked but you should be aware you’ll need to redo your personal preferences and I think you loose any favourite you may have saved.
John doggett-williams