Day 1 of the Month of Nix, year 3000
If a tree falls in the forest, and no one is around to hear it, did it really fall?
Similarly, if a species goes extinct on Earth, where do they go?
The answer is actually simpler than you might believe: they go to Earth, Reborn. Known by its residents as Nova Nativitate (often shortned to Novanati), not only do these species thrive in a seemingly infinite world built for them, they are also sapient and form their own societies. There is no species hierarchy among the sapient species; none is considered above each other. Food is provided in the form of non-sapient extant species, which appear and then disappear as if willed away by an invisible force.
No humans have ever set foot in Novanati, but when a little girl wishes away herself and her five abused friends, a higher power listens. And that higher power brings them to Novanati. Adopted by a pride of Sabers, they just might find that this world will mean more to them than anything on Earth. However, without any real knowledge of how they got there and how to keep other humans from entering, their very presence in Novanati may mean disaster for the entire world.
But that isn't important yet, is it?