If you have blood on your fletchings, surely it was a passthru. That's what I would guess, anyway. It would be hard for you to hit high enough to miss the lungs without going over the spine. May have done that, and if so, you won't be finding him dead anytime soon. If it was a little farther back than you thought, and behind the lungs, he will take some time. What kind of blood was on the arrow? Intestinal material, bright red or dark red?