Street photography - Missing a Great Shot

It was a Friday afternoon, lunch time. I was on the phone, walking the streets down-town in Rotterdam. It was lovely weather with that type of "spring light" that feels really fresh. My camera was safely put away in my money belt. And then, out of nowhere in the pedestrian area there came four strong men, carrying a small plane from a merry-go-round on their shoulders. The light, the cheer on the men’s faces and the plane in the middle of a street full of people; it was just amazing. Before I ended my call and got hold of my camera, the plane had already disappeared in the back of a truck. It all happened too quickly. I was happy that I saw it, and at the same time angry with myself for not being quick enough to capture it with my camera. It could have become one of my best shots. How long will it take before I have forgotten this mishap? I'd better go out, enjoy the weather and assure that I have my camera ready ... always!