I just ran into this same sort of thing: had opened up a second Safari window (did so inadvertently from within Safari) and i the process of trying to close the inadvertent window, found that i had clased BOTH my Safari windows. And when i had re-opened Safari, instead of seeing all the tabs i’d laid out last night (sure, too many, but …), they were ALL gone.
I did check my Settings / Safari options - not set to expire for a month - so shouldn’t have lost last night.
MacOS offers a “re-open recently closed tabs” feature - but not seeing that in iPad.
I think this is now the second time its happened to me in a few weeks - the first time i wondered if i was just losing it a wee bit, but this time i’m sure i repeated the sequence of that last time - starting with trying to remove an inadvertently opened a second safari slideover window.
Others seeing this? And have a suggestion for tab recovery - other than rummaging thru History and trying to remember what i had open?