There are a lot of asteroids in the Solar System. Millions. The solar system is huge. It's not laughable that this one wasn't seen - it was extremely tiny.
Most asteroids that we can detect we do not have the technology to deflect unless we discover them decades before impact. Even then, deflecting them is all theoretical and would be a monumental technological undertaking, as it has never been attempted before.
Most asteroids that we can detect we do not have the technology to deflect unless we discover them decades before impact. Even then, deflecting them is all theoretical and would be a monumental technological undertaking, as it has never been attempted before.