(Seaside, OR)  --  A boy remains missing after being swept out to sea in an incident that killed his sister and left their father hospitalized.  Authorities say the father and his two children were swept out to sea Saturday afternoon during a king tide near Cannon Beach.  Rescuers pulled the father and daughter from the water and rushed them to a hospital, where the girl died.  The Coast Guard spent five hours searching for the boy Saturday before calling off their search.