A similar thing happened to my mother in Southampton generals intensive care unit. Luckily she survived but in her case it turned out a less that ideally qualified member of agency staff had reinserted her feeding tube but just put it straight into her lung. Luckily it was found during a scan but only after 4 hours. It could have been much worse if she had been older, weaker or it had remained undiscovered for much longer. My sympathy to everyone affected in this case.
One thing you unfortunately learn if you spend much time in hospitals is that unless there is an independent witness to an incident you very seldom get the full truth.