This event reminds me of the similar story I was told many years ago...
I was at the Boeing plant in Seattle, picking up some AOG parts for my former employer - Worldways Canada. At the time of my visit, the Boeing shipping department staff were also shipping a new 737 cockpit door, as a replacement part. There was great amusement, as this was the first time a cockpit door had been requested as a replacement part (it had to be specially made). Turns out that Captain stepped out for a bio break, and first officer stepped out for a coffee before the Captain returned. Door locked behind them, cockpit unoccupied. They apparently beat their way in with a fire axe, in view of the passengers. Hence the need for the replacement part. At least back in those days, the door was not that hard to get through!