I had a whole bunch of open Firefox tabs and tab groups all carefully arranged just the way I wanted, then somehow a couple of tabs got moved to a new window (don't know how that happened, I didn't click the "Move Tab" and "Move To A New Window" menu options), and when I was trying to figure out how to move them back (not possible, apparently) the original window got accidentally closed -- and with it all my tabs and tab groups! When I reopened Firefox they just weren't there. Aagh! Clicking on History just shows the last tabs I accessed, not the full arrangement of groups and the many other tabs I haven't accessed in awhile but want to keep at the ready.

Can I get all that back? Or was relying on Firefox to organize my online work a bad idea?