IMPORTANT!: Watch the video above before reading the rest of this post.
Don’t feel too bad, the majority of people miss it. The phenomenon occurring in the video above is called Change Blindness. It happens because although you were looking closely, you weren’t seeing.
Attention is required to identify changes. If your attention is distracted, then it’s very easy to miss large changes in your environment. This flaw in our vision is what countless illusions and magic tricks rely on; distractions that keep us from seeing what they’re really doing.
The limited resources of our vision allow us to focus in on certain aspects of our environment. However this leaves gaps which are filled in by our expectations. When you were focusing on the passes made by the team in white, you had no reason to expect a moonwalking gorilla to be passing by. Therefore, you missed it.