A good hit will leave a dead deer. If the deer wasn't found with such an exhaustive search then more than likely it wasn't as good a shot as you think. If the broadhead was sharp and its put into the vitals the story ends with a recovered deer.
Every hunter I know loses deer from time to time. It happens. Just keep taking good shots and you will find most of them without a string tracker. I also commend you on looking for the animal like you did. Many give up too fast.