Someone mentioned them being gone. Looks like you'll have to add them again. If you made backup then just import them back up.
I run mine in Chrome so I cant specifically speak to this other than it has happened to me before but not lately. I also run Firefox and lately I have had nothing but problems with it and it all started with the update to 55.x.x. Any time I restart my computer I lose all of my pinned tabs and have to go in and manually close them and load it without addons and then restart the browser before I can pin them again. I dont know if it is a rogue addon or if it is something with Win 10 which incidentally will not update for me either, even with a fresh install I cant get the latest creator updates. I suppose I could disable all of my addons and add them back one by one, but that is a ton of work. Back to you as some said if you have a backup then just import it. What I like to do is run CCleaner every week or two and before I do that I backup TM, Hit scraper, Panda Crazy and Hit database. Also a good idea to either save those to the cloud(dropbox, OneDrive, Google Drive, etc..) or to a usb drive or both. I keep a few different backups in several places.
image tests-please ignore http://i1066.photobucket.com/albums/u404/photob32/Frogs%20Forever/2%20frogs_zpsalc1awja.jpg image test http://i1066.photobucket.com/albums/photob32/FrogsForever/zpsalc1awja.jpg http://i1066.photobucket.com/albums/u404/photob32/AAA--LIFE/smiley--blanket.gif