Where does Safari store the open tabs? I'd like to know where does Safari store all the open tabs. My daughter did who-knows-what on my laptop and all tabs were closed (except hers of course...) and the "Reopen from last session" is greyed.

I know that when I update Safari, or even upgrade the OS, the open tabs are kept. I then suppose they are stored in a file somewhere on the HD. As I do have TimeMachine active, I hope that by restoring an older version of this file, I would be able to retrieve my open tabs. The problem being of course that I don't know where it stores them...

I'm on Safari 13.0.2 on macOS 10.13.6 (High Sierra - can't upgrade my early 2011 MBP, but I don't think it would have changed something)
OK, just found it!
I closed Safari, restored the file ~/Library/Safari/LastSession.plist from my TimeMachine backup. I then restarted Safari and hit the "Restore from Last Session"

What a bliss to see my 71 tabs back to life!