You act like they all knew about the portal between Termina and Hyrule. (And, once again, species differences.)I considered yesterday, what else the postman thing could have meant. Even if Termina isn't under the ocean, there's a chance the people of Termina were still a part of the flood.
After all, Termina nearly all-out evacuated. Where did they evacuate to? Not many places to disappear to when the World's going to be destroyed.
Just a thought.