Well, I have clicked undo but it's still not picking up my original
document. I've saved it once, but never closed the window.

The good news is that luckily, I had sent an email that contained the
original document (mostly!) to a colleague last night. So... I was able to
retrieve that and restore from my email program.

So, it sounds like it I've clicked undo as far as it can go that's all I can
do.. Unless I did the backup copy via tools (which I did just now. Thanks to
all for that tip!)