No, I don't think anyone expects you to do that. However, if you were already in your car, you would look out for it. Everyone isn't in bed during the 3rd shift. I don't think emergency messages were meant to be silenced. Pick a person in your life that means a lot to you. Say something tragic happened to them and someone needed to notify you personally regardless of the hour. Would you want the message to get to you at 2:52am, silenced, and then when you get up at 8 or whenever you look over and say "Oh my mom was kidnapped 7 hours ago, but I sure got a good nights sleep"
(hope nothing like that happens to you...speaking in general)