It was photographed by tourists and detected by Air Force satellites. Had it continued on into the atmosphere, it could have caused a Hiroshima-scale explosion over Canada, somewhat smaller than the Siberian blast. Even larger objects have hit Earth, but they are more rare. Brick-sized interplanetary stones fall from the sky in various locations every year. Several houses and a car have been hit in recent decades.
Interplanetary space contains many small bodies of different sizes.
All of them move in elliptical orbits around the sun as prescribed by Kepler. Occasionally their orbits intersect those of planets, leading to a collision. Large enough bodies leave sizable planets or satellites. This explains why impact craters are present on surfaces of planets and moons throughout the solar system. If we continue to study asteroids and build more telescopes for detecting and tracking them, we will have better information about the frequency of such asteroid impact-explosions, and more chance to have warning about impending impacts.