Tough situation - I've been there.
You'll feel better if you go back and look again. Don't look for blood sign, look for a dead deer. Think "if I were a wounded deer, where would I hide?" Keep your eye out for crows, or other birds that might feed on a dead animal. Look in the thick areas near water if you have any.
Finally, learn from the experience like others have said. Deer are amazing animals in their will to survive. A deer even with one lung hit can live, if not discovered by predators. A non lethal pass through, (especially brisket area) is hardly a problem for a deer to survive.
As far as what type of blood from the hit - Dark blood is rarely a good sign - it comes from veins, from blood vessels leading too the heart - sometimes the liver. Sure some veins are deadly when hit - but most have little pressure, and will clot quickly. Bright red blood is from an artery, or the lungs. Just clipping a main artery like the femoral, aorta, or coratid, will cause a deer to expire quicker than a lung shot. This is because its freshly oxygenated blood under massive pressure, that is required for systemic function. Sprays of bright red blood indicate a lung hit, as the lung function forces blood out an exit, or even an entrance hole. A deer spraying blood to one or both sides of his trail will not go very far.
Still its tough, and can even make one want to not hunt for a while, afterall, we strive to take the animal cleanly. Get back up on the horse, and truly understand what went wrong (too far, bad angle, followed too soon, dull broadhead, etc.)
Good luck the rest of your season.
Edited by - farm hunter on 10/01/2002 23:02:08