Pythons in general, and ball pythons in particular, do not rely on their eyesight for hunting nearly as much as you might think. In general predators are thought of as relying on eyesight as their primary sense.
Pythons rely on heat pits first. Jacobson's organ second. Eyes third.
This is why feeding reaction strikes occur. Little baby BP things your hand is a rat? Kingsnake tries to swallow your finger? They sure aren't using their eyes very well.
It'd be like you closing your eyes and using your hearing to try to punch someone in the face while they're jumping up and down. Sure you'll have a good idea of where they are, and very well may hit them in the chest or somewhere else, but you won't be accurate, and you may miss or just get glancing blows.
I believe that python eyes are pretty good in a physical sense, but that their minds don't interpret the images very well and use the input to the best of their ability.
My bet is that your feeder was thawed to room temperature, and your BP couldn't use its heat pits to aim.