>So like a water bubble from a splash?
Like liquid ejecta from an impact. More like a bullet shot into sand or the water thrown up from a splash.
>what are the odds that bubble ends up so perfectly spherical it is a ball?
There's no need for a bubble. The ejecta goes into orbit. Some rains down. Some remains in orbit. Mass condensation and concentration creates gravity. Gravity forms liquid or semi-liquid matter into a sphere.
>yet no pics. strange imho.
https://www.space.com/11186-photo-side-moon-nasa-lunar-orbiter.html
https://www.alamy.com/stock-photo/far-side-of-the-moon.html
https://www.technologyreview.com/2020/01/23/276107/these-are-the-most-detailed-photos-yet-of-the-far-side-of-the-moon/