Why did all my open tabs & history disappear?

I just opened Safari, on my MacBook Pro, and there are not a single previously opened tab or window!! There's also nothing in the Recently Closed, the ReOpen All Windows from the last Session also show nothing. And even the History is empty!

I've never had every window & tab disappear, without their still showing up in those other headings, so that I could reopen them, one at a time, today it's a completely blank slate, and I have no clue as why this happened. Any ideas?

And on a side note, why can't we filter our search when looking for previous posts covering the issue we may have? Seeing posts from 10 years ago, are not going to be very relevant to the OS or version of Safari in use today...