The Chelyabinsk event had zero warning for two reasons: one, the trajectory of the inbound came out of the Sun (just like a fighter pilot would dive on his target), and two, every telescope in the world at the time was watching the other rock sail peacefully past...
Now, the impactor in the Sudan a few years before that, the same people who blew the call on Chelyabinsk were high-fiving each other because they saw that one eight hours before it hit the atmosphere.
Now, I sure feel warm & fuzzy...
Me too.