I agree with Chris, shot placement is key to consistant game recovery. But another factor is plane 'ol luck... good or bad. A few years back, i shoot a deer with a compound with all the gizmo's and the latest whizzbang broadhead. Now to my minds eye, I made a perfect shoat. Right behind the shoulder. I never found even a single drop of blood, and never found the deer. A couple years back I shot a doe with a selfbow, cane arrow, and stone point. I hit her in front of the shoulder, and the arrow latterly bounced off. The deer jumped at the shot, trotted off a little ways and started walking again. Now there was only a little blood on the point, and none on the ground, but that deer walked about 50 yards and simply lay ed down and died.
Does a stone point work? A well designed and sharp point works very well.
When I first started using selfbows, they were in the 75-80 lb range. In the last few years, I have started useing bows around 55 lbs, taking special care with matching arrow spine to the bow I'm hunting with. I actually get better penetration now than with the heaver bows.
The primitive arrow has been the hardest aspect of my hunting get up since I started useing primitive gear. A stone point not only needs to be sharp, but the design and how it is halfted is crucial as well. the arrow shaft must be matched perfectly with the bow so it leaves the bow and recovers from the paradox as quickly as possable. We've all seen arrows that fly nock left or right as it leave our bows. If a deer is close, as is usually the case when hunting with stone points, and the arrow is still not recovered fully; then penetration will suffer.
Point after passthrough on whitetail with 75 lb bow
Point after passthrough with 55 lb selfbow