Go back to where you stopped and continue to track, you will most likely find him. Never give up. I once shot a deer that dropped like a rock, got back up and ran down and across a ravine. There were pieces of lung on the ground with a lot of blood where the deer went down. I lost the trail and backtracked and tracked for an hour and then gave up. About two hours later I decided that the deer had to be dead based on the evidence where I shot her, I started all over again to track the blood trail and discovered where she had turned and changed directions that I missed the first time and 40 yards further I found her stone dead and she had a hole through her heart. Never under estimate the tenacity of a whitetail deer to live.
When you are up to your butt in alligators, it is hard to remember your intent was to drain the swamp. Stay focused!