How did you lose the file?
Office has it's own file recovery in case you lose files on a crash or unexpected shutdown and restart.
To find the files, they're in the AutoRecovery folder. You can find them in the Finder under /Users/<username>/Library/Containers/com.microsoft.Word/Data/Library/Preferences/AutoRecovery
If it was deleted then try PhotoRec
When you delete a file and want to recover it you should stop creating more files, since those files could be written on top of the deleted file and could make the recovery more difficult.