The challenge illustrates a familiar way to hide in plain sight, by being a small part of a complex scene. My response illustrates another way, by being quick and unexpected. While a classic experiment using a fake gorilla provides one example, my response uses a genuine wren.
So long ago that I was using color negative film, I took a photo of a wren feeding his/her chicks. When I eventually got the print back from the lab, I saw something I had never seen before and have not seen since:
The parent’s tail feathers fan out to brace against the outside of the nest box, forming almost a half-circle. Don’t blink or you’ll miss it. The shutter clicked at a lucky instant, freezing a detail of the momentary handoff that I have never seen in real time.
To get a web image, I scanned the old print and looked more closely at the scanned image while deciding how to crop it. A bird splat on the nest box was hiding in plain sight (the familiar way) and was now a distraction. No problem. Any decent photo editing software could remove it, as mine did.
Sad to say, all my instances of hiding in plain sight the familiar way are like that banished bird splat. Experiencing a scene in real time, I either do not notice or can easily ignore power lines, bright reflections, and whatever else detracts from the good stuff. Examining a photo later, I find that whatever hid (by being a small part of a complex scene) is now so distracting that I must tone it down if I cannot remove it.
¯\_(ツ)_/¯
The invisible gorilla experiment is a classic example of hiding in plain sight by being quick and unexpected. The resulting book is a good read exploring several ways that people often overestimate their abilities.
Mellow Curmudgeon 
