My top, bottom, ands side panels have disappeared in all Lightroom CC2015 , this is not a case of tab or tab+shift or of being switched into fullscreen mode but of the real estate where the panels should be showing panels being blacked out. I am in OS X 10.11.4
This was not happening this morning.
When I minimize the Lightroom window and then open it up again the panels are reappear until I do anything, then they disappear again. When I toggle from full to standard view they reappear briefly and disappear