Probably they came to know about the asteroid from another source. "Oooops, Russia/China/India space agency say they saw asteroid XYZ, why didn't we?" Or some

Probably they came to know about the asteroid from another source. "Oooops, Russia/China/India space agency say they saw asteroid XYZ, why didn't we?" Or some math/cosmological models say there are X asteroids floating, but they can only really observe X - 18% (which is a huge margin of error)