Most of us have been in your shoes. If you hunt long enough a non-recovered animal will happen. As stated above, most times a long blood trail is from a marginal hit or a animal that's being pushed that would otherwise lay down and expire. It amaises me sometimes how they can stay on their feet following a good hit. I'm talking bow hunting here. There is another discussion on this subject also, where we covered the many ways to decipher blood trails and sign after the shot. 2 days would indicate that the deer most likely stayed on its feet and survived despite the blood trail. Deer seem to possess high blood clotting genetics to me?I lost a Michigan bow hit buck which was at the time , I thought, a perfect front 1/3 up side shot. After a 1.5 day no recover, we assessed that I probably hit it higher than I thought, under the spine, and missed all vital organs ect. I started with two sided blood trail which became a exit only trail then nothing after 1/4 mile. It was a 0* day out and miserable time in the stand. It happens to most of us, it makes you feel pretty bad inside for a long time, however we keep hunting! Just do your best, that's all you can do!