> a space faring species encounters non-space faring species
Any non space faring species either lives on a very boring neighborhood (one where rocks never fall from the sky and other kinds mass-extinction events never happen) or is extinct and we may find their fossil remains.
As far as we know, dolphins, cockroaches, and platypuses are not space faring species. Whether their neighborhood is boring is a matter of opinion, of course.
Any non space faring species either lives on a very boring neighborhood (one where rocks never fall from the sky and other kinds mass-extinction events never happen) or is extinct and we may find their fossil remains.