Garage band merged files and now can't find wav file

Hi

I hope someone can help otherwise I've lost a lot of work

I had 2 audio file tracks A & B, both saved separately

I wanted to bring in track A to the front of track B. Normally, I just paste in the files as I use track A a lot so keep a separate file of it.

After a few attempts, it just kept repeating track B, which I thought was odd. Then, it 'merged' track A & track B and I now no longer have a copy of track B, the file is empty!

I have no idea whats happened. Typically, I finished track B today so it was the final version.

The error message is something about can't find wav file?

Help :-)