my itunes pc library got partially deleted

so today I clicked on my itunes on my desktop and there was some weird message about importing files- i didnt really pay attention, i just clicked the stop button. then when i tried to open itunes again it came up but 4000 of my 6000 songs were missing. i had to manually put them back in my library but was still about 100 short, just cuz i couldnt find the songs.

then when i tried to sync my ipod, there was a message reading "some songs on your ipod are not in your library do you want to transfer?" i figured oh good it will just put all the songs back in my library. instead, it did the opposite and took the 100 or so songs, plus all my playlists off my ipod. now i dont know what to do. help!

 

can you have Itunes scan your hard drive? maybe the other songs are somewhere else?