Missing in Mexico

Sarah Johnson is a 19-year college freshman who, along with her roommate Mary, spent an extra week in Los Cabos, Mexico after a family vacation at Christmas. Unexpectedly, Sarah's not on the plane back to Seattle, and her parents hire Stan, a seasoned Private Investigator, to find her. Even with local help and some promising leads in the town of San José del Cabo, he's unable to find her, and he returns to Seattle to inform the parents.
Months later he receives a mysterious letter from someone who says she can help him locate Sarah, and he jumps on the next plane to Los Cabos. Will this be the lucky break he needs to find her? Or will she remain missing -- Missing in Mexico?