Q.Indoor heart shape philodendron that froze
It was in the car and it was too cold over night. Can we save it?
It all depends on the extent of the damage - what condition is it in? In less severe cases, cold-damaged plants can be saved.
I would get it warmed back up indoors, water it and give it a boost of liquid fertilizer. Prune away damaged areas (if any).
In the meantime, please take a look at the following articles on how to save damaged plants:
https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm
https://www.gardeningknowhow.com/plant-problems/environmental/how-to-treat-frozen-plants.htm
https://www.gardeningknowhow.com/plant-problems/environmental/care-of-damaged-plants.htm