the deer was slightly quatering towards me and the shot entered the deer in the shoulder crease
If he was bedded and you were standing, shot was probably higher on the body. Not much chance of lot's of blood escaping this type of entrance wound unless you hit a vein or artery near the skin surface, blood loss from lung/liver hit was most likely contained in the body cavity.
and drove back through the body coming out right between the hund quarters
Rear end? again, not a major area for blood loss, plus going through the abdominal cavity probably gummed up the exit whole somewhat preventing further loss.
Sounds much more like a shot placement issue.