On another note, I shot a buck this year. Double lunged him, and the bullet shrapnel even lacerated his heart. After I shot him he ran to the edge of a tree line, head down wagging his tail. He then walked behind some evergreens and never came out the other side.
I walked to where I shot him, and to where he stopped at the edge of the tree line. I then walked to the evergreens he walked behind. This semi circle was maybe about 30 yards total distance. Didnt find a speck of blood until right at the evergreen. He was piled up under the branches of the evergreen.
Lung shots in my experience sometimes don't bleed much, especially if they are high lung shots because the blood pools inside the body. Don't,let the lack of blood worry you. I've had several deer that were hit well not leave good blood trails. They are usually found dead nearby.