Except for a few points where a pinpoint dot of grease is applied, there should be no grease in the shutter; oil is what is used on the pivots. But, 27 F isn't cold. There are many non-freezing oils and greases available which will continue working in temperatures where the human body will have long since shut down.
Originally Posted by Mainecoonmaniac
What most likely happened is some old, thickened lube was left in the shutter - virtually any instrument/watch oil will continue working at that relatively warm temperature.