CVR
One item of note from the equipment listed in the sales flyer for the incident aircraft was that it was equipped with a CVR that apparently records flight parameters as well, per the specs:
http://www.l-3ar.com/Draft_0612/html/PROD-Av-Rec-FA2100CVR.php
Perhaps the mystery will be ultimately solved. It also has a pinger, who knows if the coast guard or local authorities can detect it, or will detect it in shallow water.