Miss the vital area and a deer will bolt—but it won't drop. Instead, it will often slow to a walking pace, travel a distance, and then lie down to expire. And it will leave little, if any, blood trail.
Recovering that deer requires tracking skills, and one of the best tools a hunter can have is what I'll call a "stride stick." This is a slender, 4-foot wooden dowel with a large rubber band wrapped around it.