Official comment

Hey Luke,
Sorry to hear about that. Yes, you can recover from an export USB drive - simply connect the drive to your computer, on the DEVICE entry at the left of rekordbox, create anew playlist ON the device. Add all songs from the device to that playlist (you'll see why in a second), then right-click on the playlist and select IMPORT PLAYLIST. It will ask if you also want to import the music - say yes, pick a location for it, and you're golden. Import the other playlists on the drive to keep those playlists as well.