Well, I don't know why your iPod is showing it has no music. You're saying that when you try to play music, such as by selecting Shuffle from the iPod's main screen, it says there are no songs on it...
When you look at the iPod's content list in iTunes, either indented under the iPod in the sidebar or by clicking On This iPod (when the sidebar is hidden), and you select Music, does the song list show the songs or is it empty?
You said you already tried doing a Restore, so it's probably not a software or data corruption issue in the iPod.