When I upgraded to iOS 7.0.2 today, I noticed this message appear:
There are purchased items on the iPhone Jay Docherty’s iPhone that have not been transferred to your iTunes library. You should transfer these items to your iTunes library before updating this iPhone.
This is an unusually un-helpful message from Apple: there are too many unanswered questions here. Which items haven’t been transferred? How do I transfer these items? Doesn’t that happen automatically when I sync?
Well, the answer is simple: just right-click on the iPhone in the iTunes sidebar and choose ‘Transfer Purchases.’ Wait for it to do its thing and you’re all done!