Music from iPod touch and iPad deleted for no reason

I have a friend who owns both an iPad and an iPod touch both with the same music and synced to the iTunes desktop. However, for some reason, practically all the music from both devices disappeared. Most of the music is bought but some are from CDs put into iTunes. She has tried redownloading her music to her device but it doesn't seem to have worked. Is her account hacked or is there soem sort of glitch in her account?