Here's what I did that actually worked:
1. Make a copy of this weird .pages folder.
2. Move the copy out of Dropbox and onto your Desktop.
3. Open the folder.
4. Select ALL contents of the folder.
5. Right-click and select compress. This creates a Archive.zip file in the folder.
6. Move this Archive.zip file onto your Desktop.
7. Double-click the Archive.zip file to create a new folder called Archive.
8. Click the folder, then press Return: this highlights the name of the folder. At the END of the name, add .pages
9. A dialog box will pop up, select Add.
10. This will then revert the file back to a readable and editable Pages document!