I just subscribed to iTunes Match. I have a lot of protected songs that I want to upgrade to non-DRM. I understand that this may not be available for every song -- depending on the contractual rights. To upgrade, I understand that I have to delete the song from my library, and then download the non-DRM 256 version from the cloud. What if I delete a song that doesn't have the non-DRM version available? Do I lose it?