Hello, I have been having this issue for about a week and a half now. I do not understand what is causing it to happen. But, all my "saved" music temporarily disappears. IT is really annoying, because to fix it I have to clear my data, thus forcing me to redownload it. I am at college with shotty Wi-Fi, which makes the process that much more annoying. This is the second time it has happened. I'm on Android 4.4.4 on my Nexus 4. No custom roms, just stock.