No blood trail is probably not be a heart shot. I suspect it was high and forward from the heart, missing the lungs too. I have shot deer with bow and arrow this way in the past - it sucks! The blood trail stops and the deer keeps going like nothing happened. Now, I aim back a little dead center on the lungs so if the shot is high, it still gets the lungs - much better success rate. Lung shot is the best IMHO as it affords the largest target.

Hope you still can find this one. Don't get too discouraged. Take a look at some "deer vitals" diagrams (google images) and mentally prepare for the next shot you take.