If Zenaida exists -- wouldn't one of her friends or family come forward by now to say "I think my Zenaida may be the one"? Even if we buy the whole thing that all of Casey's family and friends were kept from Zenaida, somebody on the other side, Zenaida's acquaintances, would have seen her with the kid, at the park, at the beach, going in and our of her home/apartment.