Buried Secrets by Joseph Finder

A claustrophobic's worst nightmare. Seventeen-year-old Alexa Marcus has been kidnapped and is buried alive, her only communication to the outside world is with her kidnapper. The ransom is vague. Her father doesn't want to share with "private spy" and family friend Nick Heller, any of the reasons Lexi might have been abducted. When Alexa appears in a live-streaming video-cam on the Internet it is apparent she is in big trouble. Nick, helped with ex-lover Diana Madigan, trace down the many leads with lies, secrets, and subterfuge preventing Nick from moving forward. With the FBI after Alexa's father for information he has, the pressure from highly placed individuals is intense. A good read, thrilling, holding your attention to the end.