Astronomers almost made the call.
On January 13th, some scientists believed that a 30 meter object called 2004 AS1 was going to hit Earth. When a researcher at the JPL said the rock had a chance of 1 out 4 to hit the planet ‘somewhere in the Northern Hemisphere’, officials contemplated to make the call to the President. However:
“They completely misread the situation.There was plenty of time to get other observers on the job”
They did apparently: an amateur astronomer managed to take his telescope to the clouds and take a picture of a blank sky.