Ouch, sorry you went through that.

I don't know whether this is a cosmetic solution or not, but for me, the autosave button is on my Quick Access Toolbar, and you should be able to re-add it at Customize the QAT, All Commands, "Turn AutoSave On/Off." Of course, if that doesn't activate it, the button is meaningless. But is it possible it got right mouse clicked and removed somehow?

As for the work you've done, I'm assuming you went through looking for any recovery options such as listed here: How to recover unsaved Word documents - Office | Microsoft Learn

For better or worse, "save and save often" is so drilled into my head that I'm constantly manually saving even in a program that auto-saves.

Best of luck,

Ann