Do you trust everything you read on Twitter? A mother who has lost a child will be very stressed - a message on twitter isn't convincing proof that the child is ok so the news will cause turmoil - "Is this message true?", "Is this just raising false hopes?" - this would just increase the stress - If the mother can't then confirm it through a better chanel it could make things worse until she can, pushing comeone nearer to the edge.
In this case that didn't happen so it worked out ok but we have to think of all possible scenarios. (What we're not told is whether the mother was told to watch twitter as this might be the quickest way of getting the news - if that was the case then it completley changes the situation