Audio files disappeared from session and Audio file folder? HELP

[Wookie]

I appologize if this has allready been covered in a post but I couldn't find any where the files disappear from the Audio Folder too.
I have an external HD that I run all my session work off of. I back them up on my internal HD cause I have 2 terabite drives in the box. I did a back up from my external on to my internal and all of a sudden I lost a bunch of tracks. The regions are there in the session but are that dreaded blue color that you get when it can't re-link. There in my regions list but don't look active. I try to automatically relink and pt's can't find them. I try to manually relink and the files aren't even in my Audio Files folder now. They literally disappeared. Can any one please help me with this. Many hours of work all of a sudden lost.