Help needed! Lost files!

Hi there, I’ve just recorded four songs on four separate sessions. They were all meant to be saved into the same folder and they look like they are however two of the four can’t find the audio when I open them.

When I try to open one of the two with missing audio it asks me to ‘Set Project Folder’. Any ideas what has happened and what I can do to recover the audio as I’ll be pretty stuck if I can’t find it!!!