I've done a little googling on the subject and haven't found anything useful
so far. Most of the links I've found seem to deal with older versions of
Firefox (iiuc) which stored the history in a file named sessionstore.js (iiuc).
There is no sessionstore.js file on my computer (Debian wheezy), there is a
places.sqlite file, and it contains a little over 10 MB, and I'm assuming the
hiistory is in there.
On the Firefox History menu, all of "Restore Previous Session", "Recently
Closed Tabs", and "Recently Closed Windows" are grayed out.
One complicating factor may b this: I've had my computer, and that session of
Firefox open for quite a while (maybe a month for Firefox??), and, in that
time, there have been several updates of Firefox suggested (in/by apper), and
I downloaded them all, installed them all, but I did not shutdown Firefox so
that the newer downloaded version could actually go into effect.
The version of Firefox now running is Firefox ESR 45.4.0--I don't know what
version of Firefox ESR was running before the crash.
I've looked at the sessionrestore variables in about:config, but I don't see
anything that worries me, most of the settings are the default, only one says
it is user set, and that is:
To the best of my recollection, I have never intentionally set or changed this
value, so I don't know why it is user set. (I haven't looked at the
about:config page in years, and certainly not in the last six months.