I am going to agree with R2elk, again, on this 45 minutes is not much time for a drop.. Did you open the incubator? What kind is it? that seems like a huge drop for 45 minutes. That said the hen will leave the nest for that long to search for food and water. Ethel would disappear during incubating time for days then come spend an hour or two in the yard, until she could slip away again. She always had a hatch.
Cold is way better than hot on the eggs. If the incubator had failed to the hot side for that time, you could kiss them good bye. cold, no big deal.