Facing iOS 4.2's disappearing iPod app music glitch, here's how to fix it.
- Connect your iPhone to your computer and launch iTunes on the computer.
- The phone appears under devices in the left-hand column; click the arrow to the left of it so your media categories appear and select music.
- Play a song on the iPhone via iTunes on your computer.
- Sync the iPhone again
- Re-open the iPod app on the iPhone
- Wait a while while the iPod updates its library and then relax to your favorite Motorhead tune