I agree that this one - assuming goatboy is not a pathological liar etc etc - really calls into question many fundamental things about our so-called understanding of reality. I love it!
The moon has no ring system - good thought, though.
Henry - goatboy saw it appear to come from behind the edge of the moon, circle around the front, disappear behind the moon on the opposite edge, and then reappear again on the original side. The impression being that it must have been circling the moon. The notion that perhaps it might have been a nearby bug or bird or bat catching the light in some exotic way and creating an optical illusion being ruled out by the fact that his friend on the next swing saw the same thing - a nearby creature would not have lined up exactly with the edges of the moon for both of them.
Assuming it was something in the vicinity of the moon, any physical "spaceship" would have had to be tens or hundreds of miles across to be seen with the naked eye at that distance, or else putting off a spectacular amount of light energy. And travelling at a significant fraction of the speed of light.
Doesn't fit with any known known electromagnetic or plasma phenomenon - though my most occumy bet would be with an unknown phenomenon of this type.
I see no reason to entertain the moon being hollow or artificial - first of all, that idea has nothing to do with what was observed, and second, if that's true then we actually know so little about astronomy, geology, and physics that there's no way we should be able to land a craft on the moon or put one into Earth orbit. It's just confounding a mystery with a baseless myth.
There's no way to know whether other people - maybe thousands of people - saw it also. How would we know? How many would have tried to report it, at the risk of sounding totally bonkers? Who would they report it to? Who would believe them enough to record what they said? Whose job would that be? And how would those reports from all over the globe get collated into one place?