might want to remember this one for future reference:

Russian space agency Roscosmos earlier admitted they did not track the meteorite that fell near Chelyabinsk, although several other flybys were detected by Roshydromet overnight. “Our ground facilities and, as I understand, those abroad too did not monitor this celestial body,” the agency spokesman said.
Astronomers around the globe didn’t notice the object coming either, and rushed in search of its traces on satellite images after the news spread.