The fridge part doesn't matter - the bone is cooked, and therefore not safe to feed. When bones are cooked, they become dry and brittle - difficult to digest and liable to splinter. Cooked bones should never be given to dogs - this is where all the horror stories you hear in vet offices of impactions, obstructions and perforations come from. Better to throw the bone in the trash. If you want to feed your dog bones, they need to be raw.