Why can you not bookmark the site you don't loose them.

Mark, You clearly didn't understand the issue or what "restore previous session" is. If you inadvertently closed Firefox or just want to return to a site(s) that you were viewing the last time you were using Firefox, you can reopen all the prior pages. Seems that this functionality is no longer working properly after the last browser update. This functionality still works with Safari

That function is still there, I have no problem restoring session as long as you restore them before again closing Firefox. So what your else you doing isn't what restore session is created for. I can restart/shutdown and restore Firefox session but if you close a open Firefox windows before running session again. And then open again all sessions will be gone but they will be listed in the "history" log.

Have a look at this. https://support.mozilla.org/en-US/questions/1478044#answer-1693290