We’ve seen the gravitational effect of Planet 9, but haven’t physically located it yet. Everyone’s looking for it.
From More Evidence of Planet Nine on Solar System’s Fringes: As the search for a hypothetical, unseen planet far beyond Neptune’s orbit continues, research by a University of Arizona team provides additional support for the possible existence of such a world and narrows the range of its parameters and location.
So… What if, this planet once belonged to another passing solar system? What if the fringe of an alien inhabited solar system touched the fringe of ours? And what if this planet “got dropped off” in an exchange similar to an electron exchange? What if it’s a large planet inhabited by alien life?
Would such a thing happen on purpose? By accident? What if this is a staging area for an alien invasion?