Lack of COVID-19 transmission on an international flight

Any follow-up, especially regarding retesting or full course of illness but also testing for antibodies?
Obviously, there is considerable faith put on the limited testing reported, and there is no information about illness course or antibody testing. Lastly, any information on the other, larger number of passengers, or how well the screening test used has held up (sensitivity/specificity). One would think a passenger or two might have developed Covid-19 on a flight of 350??