PREVIEW Thursday Night Mystery: VanishedWhen Amber Dubois vanished in San Diego County, a search turned up nothing. Then, a year later, Chelsea King disappeared in a neighboring town. Dateline reports on the mystery of the missing California teens.Get more newsLiveonPrintSept. 1, 2015, 4:27 PM UTC / Updated Sept. 1, 2015, 4:27 PM UTC