A tour bus stops at a waterfall. Some of the tourists mill around while a woman takes “the opportunity to go freshen up and change clothes. When she reboarded the bus, the rest of the passengers didn’t realize it was her. Instead, they became alarmed that she’d gone missing.
The driver waits for a an hour before alerting the police and then a search party is organized. The coast guard joins in and the whole thing goes on for hours.
Meanwhile ‘the missing person’ was actually helping the search efforts. At some point she figured out it was her that everybody was looking for and informs the police.

Simon Brew, the writer of this article, has a very pertinent piece of advice: “It’s always worth properly counting the number of people on a tour bus. No matter what they happen to be wearing.”

OK, that makes a lot of sense.

Still… what I find extremely interesting about this entire development is that the people on the bus, not the driver, had noticed that a person is missing but no one had observed that a ‘new’ one had come aboard…
How much time had those people spent together before this had happened?

OK, the picture I used above was shot in a commuter train – where passengers just want to get to their destinations – but in a tourist coach people tend to regain their seats after a short stop and to remember their neighbors.
So how come those vacationers did notice that somebody didn’t come back but didn’t observe the stranger?