I don' t know, but I had the sam experience last season with my black powder rifle.

here' s my story:

I was walking down a logging road that was just off to the side of a field. I looked out to my left as I moved along slowly, and I saw a small doe (90 lbs. I' m guessing) running along the edge of the field. She crossed over into the woods about 15 yds in front of me, and then onto the logging road. She was down wind, and smelled me almost immediately, but froze in the middle of the road. Normally I wouldn' t shoot such a small doe at the beginning of the season, but since I was still looking my first kill with my " smokepole" , I decided to take a shot. I had a 250 gr. JHP loaded over 100 gr pyrodex. I put the sight right behind the front shoulder and pulled the trigger. When the smoke cleared, I could see that I hit the deer (or so I thought), as she was laying flat on her side. She got up though and took off crashing through the woods. I never found one drop of blood, thus no deer.

Now I' ve shot deer with similar loads to this black powder one (44 mag JHP and 45-70 JHP), and both of them gave me buckets of blood to follow. I' m certain that I hit the doe, but I have on idea as to why I never found any blood.