What happened to Firefox's "Restore session" feature?

[arsivci]

App menu (rightmost hamburger) > history > restore previous session.
Also,
Alt-key > history > restore previous session.

[RLynwood]

Lately, Fx has crashed a few times, and each time I call it back up again, it comes up blank. I have it set always to remember all tabs. I've known of the "restore session" feature--a real godsend--for a long time. Lately, however, I can't find it. Looking for in on the 'net, I get hits saying it's in History; that were it was before except when it crashed. Then when I called it up it would have a highlighted button-like popup in the upper, right order asking if I want to restore the session. That always got it back, and I was off, continuing from where I'd left off before the crash. Now I can't find a "restore session" link anywhere. Why? What happened to it?