A question:
Is it also possible that the loss wasn't visible; that the cowling hadn't been positively identified as belonging to that particular aircraft and it was not possible to verify visually that it was lost?
I ask (as mere-SLF) because surely if it were visible a passenger might have called the loss to the attention of the crew, and because if it were the sort of event to trigger an alert on the deck it would have been spotted early in the flight.
Could it be that the warning to the pilot was that such an event had happened and that there was no indication was present to identify the particular aircraft.
Please forgive any abject ignorance behind the question.