iOS5 itunes library issue

Hello, I just upgraded my itouch third generation to iOS5 and i lost all my music. When i hook up my ipod to my imac it recognizes that my ipod is synced with another library which it is since i got my music from my friends laptop. All of my apps are still there except i have to install them again but i was wondering does anybody know how i can get my music back? I did a reboot but it didnt do anything for me. I am figuring since my apps are there though not installed my music must be there as well since my itunes is recognizing that my ipod is synced with another library.