If the document "somehow got saved over" and you have not been tracking revisions, you are, unfortunately, out of luck. You may wish to use a much older operating system, like VAX/VMS, that automatically saves however many previous versions of any file regardless of file type. You are always asked to confirm when you attempt to overwrite something. The computer cannot protect you against your own mistakes if you do not exercise due care. Sorry.
What version of word are you using.
Go to word -- About word -- the version will be listed.