When you open a Document file and you type something and they try to close the file, you are asked if you want to “Save” or “Save As”.
If you click “Save” then the original file is changed to include the new wording, even if the wording is incorrect!
If you make a mistake and then click “Save” you have overwritten the original file.
Unless you have a Back up of the File, you can rarely undo and roll back the Change to retrieve your Original File.

For this reason, I ALWAYS recommend that you select the “Save As” option, which will create a second copy of your File.
You can then edit your new File and have the peace of mind that the Original File is retained and not deleted.
If you are asked if you want to “Save Changes” and click YES, then your original file is overwritten.

Eg if your File is called Article.doc, then change the Save As file name to Article1.doc, so that the new copy makes sense and you can easily find it again.