You of course are coming at this from the point of view of a Human that probably believes that we (Humans) are the only recognisable, and allegedly intelligent

You of course are coming at this from the point of view of a Human that probably believes that we (Humans) are the only recognisable, and allegedly intelligent life-form in the part of the galaxy that we can just about reach. Who's to say that the Tardigrades haven't been planning a rendezvous with their lunar contacts and took advantage of the free ride? Once Mankind start mining minerals on the Moon (as they allegedly intend to), they may meet with some unexpected visitors!