the same thing happened to us last sat. we arrowed a bear at 25 yds , complete pass thru just behind the shoulder, we recovered the arrow and after about 30 min we started tracking him, caught up to him about 200 yds later , couldn't see him but he was growling and moaning loudly so we backed off to wait for another hour . started after him again and he had taken off straight downhill into the thickest hellhole that I've ever been in.we tracked him on our hands and knees where you had to push your bow thru and then belly crawl to get thru for over 4 hours, it finally got to where the blood was only a speck every 10 or 12 feet so we finally gave up.All I can figure is that the shot was above the lungs and below the spine causing a wound that didn't bleed well and I feel the bear survived. When we were at the end of our tracking the bear doubled back and waited about 10 yds above us and then took off downhill again leaving no blood trail that we could find. we figured out that we had tracked him for about a mile and the only way we were able to locate the intermitten blood was by looking for scuff marks on the ground or thinking if I were a wounded bear which way would I go, next weekend we will go back and try again.