…when they missed their embarking deadline they weren't allowed back on, despite the ship still being at anchor.

Something analogous (but less serious) happened to me a few years ago. After my parents’ funeral, the feeder flight (on the same airline) from a small city in northern Pennsylvania down to Philadelphia was delayed a bit. Got to the gate for the connecting flight to Minneapolis and they wouldn’t let us board even though the plane was still attached to the boarding ramp a hundred feet from us. The doors had been closed. No exceptions. Fifteen minutes later, the plane moved away and headed for the runway.

I was resigned to sleeping in the airport and catching a flight the next morning, but my niece is a former flight attendant who knew who to talk to and what to say. The airline put us up in a nice hotel and we drank too much in the hotel bar but made it back to the airport the next morning.