I have seen an issue where the person's songs are all in iTunes match, they've just upgraded to iOS 6 (by getting an iPhone 5, but I'm not sure it's an iPhone 5 issue). With iTunes match in iOS 6, apparently songs are not getting physically stored on the phone, and certain accessories don't see them, e.g. the ones that give you a menu to browse through the list of songs and playlists on the device. It's really hard to track down, cause you take the phone out of the dock and look at the music app and all the songs are there and you can play them, but they don't appear on the display of the accessory. What's worse is now there's no indication that they're NOT stored on the phone, because the cloud icon went away. You can only tell that they're gone when you go airplane mode and then run back to the music app and the songs are all greyed out.