Kinda late chiming in on this, but I wanted to correct a misconception. When shooting downhill or uphill, the bullet doesn't rise - it still flys in the same arcing trajectory. What gets shooters in trouble is the range. When you measured the shot with the rangefinder, you were measuring the direct distance to your target. A rifle bullet only cares about the horizontal distance to the target, so depending on the angle to your target, the horizontal distance can be significantly shorter. A bit of "simple" trigonometry can be used to figure the actual range. I've even heard of some who hunt in such terrain carry or memorize tables to figure the horizontal range to their targets for just this reason.
In this instance, if the measured range was 100 yards and the actual horizontal distance was around 60-75, the bullet still should have hit the kill zone, so I think the theory of hitting and obstruction on the way is the most probable reason for the miss.