RE: What Happened?
From your description it sounds like a one-lung shotto me. Bumping a one-lunged deer significantly reduces the chances of recovery as once they have layed up for a bit they often begin to clot up and the blood trail diminishes just as you described.
A bow shot deer often has no idea what just hurt him and isn't all that alarmed and simply beds up, but once you bump him by tracking too early he quickly realizes it was a predator that caused him harm and will run as far as his stamina will take him to escape you. The chance of recovery now is dependent on the amount of blood loss before he was bumped. You need to expand your grid much, muchfarther on a one-lung deer.