Ok here's what happened... for anyone getting a thing like this... (and don't have smoking some pot... cause it's a little bit complexe;) in a folder where I putted all the songs for the same album, I had 2 o 3 songs which were in a "folder" format (not in a package) but the song I'm taking about where all files were missing was created in a package format. 2 or 3 day ago I decided to save all the songs in that folder in a "package" format. So those songs re-saved in a package format works well because the waves of each songs has been saved in their pack, but i realized that since the first songs created in this album folder, all the waves files from the songs in that folder were saved in a more "general folder for all the songs called Audio files folder. Since I had "copied" the audio files in their package when re-saving them, those were fine, but the first was still putting all the audio files in the more general "Audio file" present in the album folder where all the songs were. f*%@... so anyway I found them! In an older version in TimeMachine, when I hadn't put the "folder songs" in package forms... anyway... I have trouble understanding myself, but good news I can just copy the audio files in the "problematic" song pack where they should be. And I'll go take a nap.... thanks!