Just speculating, but I wonder if the act of drawing it skyward is the culprit here...
You had your bow set for a specific draw length, I assume one that would fit you when you are at level full draw. When you lower your bow arm instead of bending at the waist, it has the effect of shortening your draw length. It makes sense to me (and I just tested raising and lowering my arm extended to imitate full draw) that when you raise your arm above level, it effectively increases your draw length.
I'm guessing that's what happened. When you had your bow arm up to draw, you're draw length was longer, but the bows was not. This allowed the string to come out of the cam groove enough that when you leveled off and shot, it came out of the groove.
Barring that, voodoo magic?
