That's the way a blood trail goes a lot of times. It isn't a steady stream all the way to the deer, it will start, stop, get heavy and peter out. Even a double lung broadside shot might not leave a lot of blood. Sometimes you're on your hands and knees following a track, or broken twigs, turned leaves. When all that fails you just start going on your gut and checking places they would lay up. In a swamp that could be almost anywhere including collapsing on the far side of a log they tripped over and ending up in the water with nothing but an ear sticking up.

Hunting around a swamp it tough, I've had some of my hardest trailing jobs in the last few years in the headwaters of the Black River, hence trying to get a dog trained up to help.