Have you used the program's Replace Footage to try to get back your file in the opened project? Right click the wrong file in the Project Media and select Replace Footage, followed by going to where you know the correct footage is. Have you tried that?
You may want to check out the following Adobe Tech Note on Troubleshooting Damaged Premiere Elements projects
I would have to think more fully about the situation that you are describing.
Looking forward to your follow up.
I love you.
I mean... what you suggested actually did not work completely... It replaced the clips with the correct file, but it was the full, unedited version. So I'd pretty much have to start from the beginning as far as editing was concerned. I was all ready to say, "Thanks, but it didn't really fix it"... until I clicked undo. Then, instead of going back to how it was a second ago (before I replaced the footage), all the correct, fully edited video and audio were just there again! For no apparent reason!
I think my computer is just messing with me. It's been known to do that. >_>
Even though I have no idea why or how it worked, doing what you said to do, then undoing it, fixed it! So, thanks so much!!
Thanks for the great news of success.
Just a quick just in case note, "Have you seen the Adobe Tech Note on Replace Footage?"
Although the reference has Premiere Elements 11 tones to it, the information I feel would be applicable to your version 9.0/9.0.1.
Good troubleshooting. Continued success.