Earlier quoted context omitted.
The stress of being arrested and threatened with years in prison if you don't remember your passcode could very well cause someone to forget it.
A few weeks ago my house sprang a massive leak in the roof during a rainstorm, just as I was preparing for a week-long business trip. I got so stressed, the next morning I forgot the passcode I'd been typing into my iPhone for the last five years. Three days of carefully writing down my attempts didn't work—I hit the ten-mistake limit and the phone auto-wiped.
I ordered a new SIM card which was luckily enough. But sometimes you store something in muscle memory, not number memory.