Oh my, I get the impression you’ve lost the original file. So frustrating!
I’m sorry I can’t help you with your immediate problem, but Blender has a feature you may not be aware of that can help avoid losing your hard work like this.
Every time you save a file, save it as a new version. Blender makes this easy by clicking the plus sign in the save window as shown below.
If you put a version number on the first save Blender will respect its format, but Blender will append a version number in any case. Sometimes I end up with dozens of versions while developing a project, but they’ve sometimes been great time savers! Later I can always go back and delete the old versions when there’s no need for them anymore.