Firstly I thought the update deleted my not-from-itunes-store-bought music files, then I checked the iTunes, the status bar of my iphones indicates that there are exactly 13.6GB music files on it. It appears that the mediathek file on the iphone has corrupted with the update, or maybe the update has changed the structure of the mediathek file and forgetten to update it.
What can I do? Sure, completely restore is one way but also the last way I wanna go. So I've googled around for a while to find out a better and smart way to correct it. Then I found this article [iOS 4.2 bugs: iPhone music gone after the update? Here’s the fix! ]. Okay, i am not the only one and iOs 5.0.1 is also not the only one with that bug.
- Grab your cable and plug your iPhone into iTunes on your Windows or Mac PC
- When your iPhone shows up in the sidebar, make sure you can see the content listings beneath it (click on the triangle to the left if not)
- Click on music
- Pick a song
- Play it in iTunes
- Sync your iPhone
The method in that article didn't work for me for the first time. I have to figure out why it doesn't work. The reason behind that method is: Change the play count for a song, then iTunes changes the mediathek file on the iPhone.
So it is very important for that method, just try to play a song and maybe you can forward it very quickly to the end, make SURE that the play count of that song changed and resync!
Things are gonna be alright and we don't know when apple will fix that long-lasting bug.