[2023] ironman savefile not showing up in game, please help!

That file is entirely blank I'm afraid, so there's no rescuing it.

Not sure why it has Backup in it, but is there any other save you can revert to?  

Wow, that's pretty bad. I have no idea what could cause that, I'm sorry, except you'd think it would have to be a game bug.

What I suggest for the future is you make a manual copy of the save file just before or after each play session, so you have something intact to revert to.  

I see, I'm now quite confident that led to your problem!