Exclamation point next to several songs, songs disappeared

Hello,just recently I have discovered an exclamation point next to 5 or so songs in my iTunes library. I double click the exclamation point to locate the song file, but I can't find it anywhere. Yes, I have checked itunes media>songs>artist>album> and the song is not in the album. it seems the songs have completely disappeared from my computer. The odd part of it is that the songs are on my iPhone and intact. I have tried the "transfer purchases from () iPhone" And it just says "waiting for sync to start" then "waiting for changes to be applied" and goes back to the apple logo. The songs don't get transfered to my library. Help please, I am absolutely clueless as to why this is happening