It's not that these two don't care, it's just that they both received so many messages they haven't looked at the most recent yet either because they're trying to look through them in order, or because he typically gets that damn many pointless messages from his sister so god help her if she ever actually tries to get his attention by phone in an emergency. It's like a weird variant of the boy who cried wolf. The girl who called and texted so much you can't reasonably go through them all.