A gut shot will always kill the deer. If the blood loss does not kill it, then it will die from a terrible infection. It certainly is not a pleasant way to go. Animals tend to go to water, and will also tend to avoid strenuous activities like jumping fences or in many cases even walking up hill. If you lose the blood trail, check all fence lines especially in the lowest lying areas such as a creek bed or a small ravine, etc. Like someone already mentioned, if you see particulate in the blood, you hit the stomach or the large intestine and are in for a long day, but the deer is in for a much longer one.