Theories are meant to explain something that is not directly observable, or to predict its behavior.

For an item that one can observe, there is no need to theorize. You can see it, it is there.

This may seem like it begs the question, but really you're trying to apply a framework to something for which it isn't applicable.

A theory would suggest, for example, that Pluto will be in a certain position at a certain time. You can disprove the theory, obviously, if Pluto isn't in that spot at that time. But once you can observe Pluto, you don't then need to "prove" that observation.

So, you "prove" a theory, but you don't "prove" an observation.