You might want to look into the case of Barbara Jane Mackle. She was the daughter of a wealthy family who was kidnapped in Georgia. Her family lived in Miami, and the kidnappers were a male/female team who worked for the University of Miami.

The kidnappers had constructed a crude wooden coffin before the kidnapping & buried her alive until the ransom was paid. She was buried with a small air hose, water, and little food. The FBI rescued her in time, and the culprits were caught.

When I was a student I had a part time job at a local department store during the Christmas holidays. One day I helped Barbara Mackle, but didn't realize who she was until she handed me her credit card. Of course I didn't mention her ordeal but immediately recognized the name.

I think there are some similarities between the two cases, and perhaps a quasi-copy cat who took elements from different kidnapping cases and movies but wanted to write his/her own script.