I came across this rather intriguing article earlier today, and it started me thinking about the whole way that memory works. This phenomenon of large numbers of people vividly (and honestly) 'remembering' something that didn't happen seems remarkably common.
When I was a reporter on my local newspaper, back in the early 90s, I covered a story in which a metal detectorist from a nearby village was searching for the remains of a USAAF B-17 Flying Fortress, which he remembered crashing into a hillside late in the Second World War. Other than a couple of younger blokes, though, born long after the war, he had no support in the village. Everyone else (and at that time, of course, there'd still have been plenty of people who remembered 1944-45) insisted that the plane had flown over the village, in flames, then crashed much nearer Leicester.
The man turned out to be right. The plane was exactly where he'd said it would be, and it was excavated and taken away (the wreck had been bulldozed into the hillside at the time of the crash, once the bodies were removed).
But those people who'd argued with him sincerely believed what they said. Perhaps they did actually remember another plane altogether going over in flames, although there were no records of crashes near where they said there'd be. Who knows? But it does show that you really can't trust your own mind to tell you the truth.