I dont think an open window, if the plant was inside the window, would be enough to "zap" a capensis..
IMO, the only thing that will really kill a capensis is if it's left outside in an actual frost, or the air temp actually falls below freezing..
unless the air around your capensis actually hit 30 degrees F (negative 1 or 2 C)
or lower, which is unlikely, its probably fine..
My capensis was accidently left out in 35 degree weather (+2C) this fall before I brought it inside..its fine..
A frost would have fried it..but 35 degrees (for one night only, a very short time at that low temp) didnt harm it.