The Apple Maps Nessie satellite image

Loch Ness had gone quiet. The Telegraph called this the first reported sighting in 18 months, the longest gap since 1925. All three sightings from 2013 had been debunked. One was a duck, one was a wave, and one photo had not been taken at Loch Ness at all.

Then came a picture from above. It had reportedly been captured by DigitalGlobe in January 2005, and it sat inside Apple Maps. Apple does not run its own imaging satellites. Its view of the planet is stitched together from many images.

Andrew Dixon was 26, from Darlington. He was not hunting for a monster. "I was looking at satellite images of my town and then just thought I'd have a look at Loch Ness," Dixon said. "It was a total fluke that I found it." Dixon's first thought was that it was the monster.

Together with Peter Thain, from Northumberland, Dixon sent the image to the Official Loch Ness Monster Fan Club. Its president, Gary Campbell, keeps the register of sightings. The club studied the image for about six months and concluded it was probably Nessie.

The outline was pale and ghostly against blue water, at the northern end of the loch, near Dores. It was elongated. It had what looked like two flippers. Experts speculated it could be nearly 100 feet long. "What ever it is, it's just below the surface and heading south," Campbell said.

Campbell was not easily swayed. "We've shown it to boat experts and they don't know what it is." The club took the images to Scottish Canals, who had no idea what it was. Logs and seals could not account for the shape, Campbell argued, and for an object that size the only other answer would be secret submarine trials. Monster hunter Mikko Takala still believed it showed a creature swimming below the surface.

The story broke on 18 April 2014. It did not last long. On the forum Metabunk, users laid the shape beside other boats on the loch. Mick West said it "looks exactly like the wake of other boats on the loch, just dimmer." At Southern Fried Science, Andrew Thaler found a matching boat in an earlier image, "heading south from the very north end of the Loch."

Thaler's explanation was simple: "Stitched photos aren't perfect." A low-contrast frame with the boat had been blended with a higher-contrast frame without it. The boat vanished, but its wake remained, with surface texture showing through. What was left, in Thaler's words, was "the ghostly blue outline of a boat." Metabunk user jonnyH named a suspect, the tour boat Jacobite Queen: "I'm pretty sure this is the culprit."

Benjamin Radford called the image "a composite of several different images, each with a different contrast." Overhead views and unfamiliar scales mislead the eye, Radford argued. A tantalising image sits in a Goldilocks zone, "just clear enough to give an idea of what it might be." The Daily Dot suggested Apple's processing had blurred out details. No one accused Dixon, Thain or Campbell of faking anything. Critics saw a misreading, not a hoax.

Apple did not respond to a request for comment. Apple executive Phil Schiller reportedly tweeted the story as a joke, which helped it spread. The case now has its own section in Wikipedia's article on the Loch Ness Monster. It endures as a lesson in how one satellite frame can become a creature. And how quickly the missing boat can be found.