I have checked all the possible spawn locations for snow-covered and dirt-covered objects multiple times using Dulfy’s guide. I could not find any; where they should have been, there was usually a wooden plank or some other thing.
This is either means :
1. The spawn locations were changed from Dulfy’s guide.
2. The items are bugged.
If it’s a bug, this bug halts progress and will stop people from completing the limited-time Living Story achievement.