1. Load the music that is on the Laptop onto the desktop and then sync the iPhone
2. Use something like iRip to move the music from the iPhone to the desktop.
Either way it involves making the desktop contain the same tracks as the laptop and the iPhone.
My iPhone has a large number of albums on it and not all of those albums are in my desktop iTunes Music Library. How do I move albums from the iPhone to iTunes or sync it so the music on the iPhone ends up in the iTunes Music Library?
This happened when my desktop went down and I ran iTunes on my laptop and loaded music on to the laptop iTunes Library then onto the iPhone.