I got a double lung hit on a buck early this season, and for some reason I, also, didn't have a good blood trail. It was also about dark. I just walked where I last saw him. After I lost the blood trail, I walked in circles around that area, stepping out 15 to 20 yards every full circle for about 2 1/2 hours before I had found him. He only went 120 yards or so. That would be my advise to you. My question to you is, where do you think you hit him. If you think you got a decent hit on him you should find him. If you think it was a bad hit, you're probably out of luck.