Could have actually happened - with the usual journo' spice added.
I've experienced unintentional mayday transmissions from professional and non professional pilots going through their checklists when undergoing periodical flight checks, ie at the engine failure stage.
In one case, when a helicopter pilot was confronted with an autorotation during a circuit detail, he broadcast the mayday instead of saying the words without pressing the transmit switch. Before he'd rectified the mistake I'd hit the crash alarms and the outside services auto response buttons, a bit embarressing but it proved the system works and that no one's perfect.