Monday’s Not Coming by Tiffany Jackson
Monday Charles is missing and her best friend Claudia seems to be the only person who cares; inquiries to Monday’s mother, their school, and even the police receive little response, and in some cases Claudia is straight up turned away. As events unfold and the reader gets glimpses into Monday’s life (before the disappearance) it becomes clear that her home life is a far cry from the stable family that Claudia has.