Quote Originally Posted by thegreatonemal View Post
Hydaelyn created the moon specifically as a prison for Zodiark. I'm guessing this planet just didn't have a moon at all.
As Cleretic said, it's up in the air. Figuratively that is, although also literally. Could be that the moon was created at the moment Zodiark was sundered and then simultaneously sundered itself, could be some other order of operations.

Additionally, it's worth noting that the moon can be seen in Elpis pre-sundering. There has been plenty of time to correct this obvious issue if it was indeed a bug, which may suggest that it's intended.