Unless you slept through the whole of yesterday, you may have definitely heard that the new iOS 4.2 update for Apple devices is already available for download over iTunes. The update introduces users to a number of new features. But as several users have been noticing, this update seems to be causing all music on your iPod app to vanish. Users launching the iPod app on their iPhone or iPod Touch may find that their music library no longer exists.
Apparently, this is a bug and it doesn’t actually deletes your music library. Instead, it only stops from showing them. To fix this, carry out these following steps
Step 1 : Connect your iPhone to the computer and launch iTunes
Step 2 : The iPhone will now be listed on the iTunes sidebar. Click on the arrow besides it and select Music. Playing a song on iPhone via iTunes should play the music on your computer.
Step 3 : Now, sync the phone again
You are done. Disconnecting iPhone and relaunching the iPod app should bring back all the lost music. Did it work?