Favorites disappears from sidebar in Finder
Solution 1:
Try simply hovering over the heading "Favorites" in the sidebar and then on the word "Show" which appears to the right
This toggles the favorites on and off...
Solution 2:
Hold together Option+Command+esc and then relaunch "Finder" that will solve your problem instantly. If the problem persists, please try reinstall Mac OS X by Command+R after rebooting.
Solution 3:
I've just wanted to share what has just worked on my system (10.12.6):
sudo killall sharedfilelistd Finder
and my Favourites are back.