itunes help

this is my first post. i have a macbook pro that i bought back in february. i enjoy it a lot. however i have lost a couple songs from my itunes library and i can't seem to find them. heres the story. i accidentally created a playlist from my library. i was trying to sync a new song i had purchased. so later that day i tried to resync the entire library back onto my ipod shuffle. its not a big library at all. anyway it took me a few weeks to notice, but i am missing two songs. i go to my library on itunes and it shows 1 of the songs with an exclamation sign next to it. i double click on it and it says it can't locate the original file. it then prompts me to locate the file. i try, its listed under the list of songs, but isn't in bold print like the others and i can't select it. now i went back to itunes just to see what would happen if i tried to repurchase the songs. itunes says that i've already purchased the songs, do i want to purchase them again. i decline. the second song is gone, i can't find it anywhere. not even on my library list. itunes does however also recognize that i have purchased this song as well. so what do you think is my problem? my computer is not full of anything. i've checked documents and i can't find them. any help would be appreciated. thanks.

Have you tried using Spotlight (magnifying glass in the upper right of the screen) to search for the two songs? Also, have you moved your iTunes Music folder lately?

no luck with spotlight. i haven't intentionally move the itunes folder. i did find where they should be in music, but the file had no contents. does this mean their gone?

i checked the trash, but their not there. i'm starting to think that their gone. if this is the case, what is the best way to back up my library so it won't happen again?