BowDaddy is right about the concept he speaks of. Also cmhowe is right about there being a flatter trajectory with a steep incline or decline shot. With that being said long range shooters commonly have a problem shooting short ranges with a scope. Because it's so short range you just don't practice this shot and take it for granted and forget your good shooting habits and you usually don't know where the point of impact is going to be. You probably just plain whiffed the shot. If you're going on a hunt where a short range shot is going to be likely, like sitting over a bait station, you should definitely practice those shots so you understand where the point of impact is and consider going to open sites.

I think in this case you missed low because you aimed low.