I lived through a real experience of something similar to this. On the morning of January 13, 2018 at about 8:00AM, my phone made a very loud noise, and a message appeared on the screen stating that a missile was inbound and that I should take cover. The message added ominously “THIS IS NOT A DRILL”.
I was bewildered at first, and then I began to think. There were no corroborating sirens, which Civil Defense had only that very month begun testing with new sounds for missile warnings. I immediately began to search online for any type of information that may back up the emergency message I’d received. I could find nothing.
I then decided to ignore the warning and went to my dentist appointment as scheduled. About 30 minutes after the initial alert, the all clear was announced, and it was explained that the alert had been issued in error.
My reasoning since the occurrence is that I live on an island. I cannot escape.
If an asteroid was on the way, I would want to know how certain the experts were that it would hit Honolulu. How had they arrived at their determination? Then I would decide on a course of action. By then, it would probably be too late to buy a plane ticket to another island or the mainland, so I would look for the best possible place on the island to be safe. I would try to put mountains between myself and the asteroid.