Hello Owen, Mary Patricia,
Welcome to Microsoft Q&A forum.
Google docs usually will have a built-in version history, so if you accidentally replaced it, you can rollback a previous version, please check if it is available in the document itself. Otherwise, unfortunately there are no way to recover this I'm afraid. You can try some third-party tool for this, However, most of them can only recover deleted files, not overwritten files.
Thank you for your understanding.