Grey songs appear after managing music, and seemed to be unplayable/lost. Videos lost as well. How do i retrieve them?

Question

After doing some actions with my iPod Touch 4G, ALL my music AND video library turned grey, or rather, after pressing the Music app, I received the message, along the lines of "There is no music." This is on my Mac laptop with an older version of itunes, my main music is however backed up on my desktop Mac.
Actions and settings that i took which may have caused the grey-out or loss of my music and videos.
1. Manually manage music and videos.
2. Unchecked and rechecked a song, out of sheer interest (this may be the problem) whilst on my laptop
3. Managing files inside the iPod, using another desktop application whilst the iPod was in my laptop.
The situation
All music appeared grey in my iPod
Majority of VIDEOS LOST.
Retrieved most of MY music from my Home Mac via iTunes auto-sync
Friend's music is LOST (greyed out and unplayable in iTunes)
My attempts to retrieve lost music and videos:
1. Removed my iPod from laptop and attached my iPod to my desktop Mac, and it automatically synced, retrieving the music i had. The music my friend had recently lent me, that is, put in my iPod via his iTunes on PC APPEARS TO HAVE BEEN LOST. My music is in black font on the iPod, but the music my friend had gave me is in light grey/gray font.
Where did this video and music go? Did i delete the music and videos?

Answer 1

Photos/videos in the Camera Roll are not synced. Photos/videos in the Camera Roll are not touched with the iTunes sync process. Photos/videos in the Camera Roll can be imported by your computer which is not handled by iTunes. Most importing software includes an option to delete the photos/videos from the Camera Roll after the import process is complete. If is my understanding that some Windows import software supports importing photos from the Camera Roll, but not videos. Regardless, the import software should not delete the photos/videos from the Camera Roll unless you set the app to do so.
Photos/videos in the Camera Roll are included with your iPhone's backup. If you synced your iPhone with iTunes before the videos on the Camera Roll went missing and you haven't synced your iPhone with iTunes since they went missing, you can try restoring the iPhone with iTunes from the iPhone's backup. Don't sync the iPhone with iTunes again and decline the prompt to update the iPhone's backup after selecting Restore.