They probably decided to take a nap. Bring up the temperature slowly to the low 60s while periodically agitating the fermentor to get the yeast back into suspension.
The Fiesty(sic) Goat Brewery est. 2007 & Clusterfuggle Experimental Ales est. 2009
Primary: Brett Saison, Brett Berliner Weisse, sLambic I, sLambic II, Pils, Dunkel, Oud Bruin
Secondary: Flanders Red I, Cab Merlot
Kegged: Porter, Scottish 80, Pils, Orange Blossom Mead