I was cleaning up my Firefox by deleting some bookmarks from a few windows (yes, I have far too many tabs in too many windows). But all seemed OK when I logged in again EXCEPT that one window that I use often was just gone. I had only deleted one tab from it, but now that whole window is missing. Is there some place I can recover the missing ones from? Macbook Pro running 10.12.6 Firefox 69 (it is about to auto-update to 60.0.2).