I hate to hear that. I hate to see a good animal wasted but, when you do your best to take a good shot and then do the best tracking job that you can, then you have done all that you can do. It happens to the best of us. I tracked a doe one year for about eight hours, and over two miles through woods and swamp land. The blood trail finally just ended, I never did find the deer. Now I try to be sure to take a good shot, I don't try "iffy" shots or shots at running deer, then I look the area over with a fine tooth comb, that's about all you can do! Better luck next time!