Any chance it was close to the window and got too cold?
Aaah! Could have done. The windows are single-paned; I've tried to protect (outside temp is hovering just above freezing) but even with the curtains drawn it could easily get down into the 50s F during the night. The plant sits about 6-12 inches (15-30 cm) from the window. I'll try moving it a little further into the room.