If you've lost your original audio files and cover art you can retrieve them again via your Dashboard at Catapult if you've purchased our Locker service.
Once you've purchased this service (Either during the submission process or even after your album is already distributed), simply login to your Dashboard at Catapult and click on the album you would like to download. Then click on the "Locker" tab and the links to download your album's assets will appear.
Sample of Locker Service