I agree with joe I don't believe you penetrated the chest cavity either from the angle you descride at that close of a distance you more than likely lodged you arrow behind that front shoulder.Think about back to the last time you quartered a deer and removed the front leg and shoulder from the body.If you were aiming and hit that crease at that angle both the deer and the height then you probably did hit that deer behind the shoulder but not penetrating the rib cage.the arrow just lodged in the shoulder,but if it is still there then the deer will surely die or get weak enough for the predators to finish the job you started.Don't beat yourself up, learn from it,if you do the same thing again then you can beat yourself up and we will help,lol.