I have no Sessionstore file at all..ever. May have deleted the orginal one in a "maybe this will work" period of frustration. How do I get it back?

Question

Using Windows 8.1, FireFox 29.0.1. No SessionStore.bak exists either. I was trying to solve the issue of pinned tabs not opening up after closing and restarting the browser.

Answer 1

I suspect that file is gone and unrecoverable. However, you could try an undelete program such as the following and see whether it discovers any sessionstore.js or sessionstore.bak files.
http://www.piriform.com/recuva
Undeleting doesn't have a great track record for finding intact/undamaged files, especially as time passes and Windows overwrites the old data, but sessionstore files list the URLs in readable form, so even a damaged file might be useful.
After that, could you check for customized session history settings in Firefox's about:config preferences editor. Here's how:
(1) In a new tab, type or paste '''about:config''' in the address bar and press Enter. Click the button promising to be careful.
(2) In the search box above the list, type or paste '''sess''' and pause while the list is filtered
(3) Review the preferences starting with:
* browser.sessionhistory.
* browser.sessionstore.
If you see bolded entries, which indicates that they vary from the default setting, could you right-click > Copy and post in a reply to see whether they might be relevant to this problem?