This is indicative that Maria's phone activity ceased on 12-14.
http://www.daytondailynews.com/stor.../10/ddn011008marineinside.html?cxntlid=inform
(snip)
Mary Lauterbach had "a very normal conversation" with the 20-year-old Marine when they discussed the visit in a phone call on Dec. 14. Lauterbach is a lance corporal stationed at Camp Lejeune. That evening, a man whom Maria Lauterbach rented a room from off the base, called the Lauterbachs to "indicate he thought she had gone someplace," said Lauterbach, assistant director of donor relations at the University of Dayton.
"We thought that was very strange so we started trying to call her and
her cell phone was turned off," she said.