if you open a word document, the file is loaded to the RAM. And ANY change to the file stored in the ram will be updated immediately. That's how RAM works. It's temporary storrage.
Even changing a sentence like "Backup is a good idea" to "Backup is important" will edit the file on the RAM.
When you hit "save" it basically writes the new data in the RAM to your storrage device.
And it will be hard to recover a previous version of a file on your storrage device (if not impossible) because they way editing files work, is rewriting the sectors on the haddrive that already have the file stored, to match the new info.
This is different from simply deleting a file. Deleted files aren't really deleted until the are overwritten. Deleting them simple marks the sectors as free spaces even though there are still data on them. Rewriting data erases the sectors and stores updated or new date.
I am sorry, but you are screwed. The reason i asked you to check previous versions, was in hopes you have activated windows File history feature. It saves older versions of a file separately.
I hope this have taught you that backup is important, and also maybe give the Windows file history feature a try.
How important was the file since to are considering suicide :/ (I know you don't mean it literrally, but i am just curious)