Where did you suppose it crashed in the Ocean...
Gulf of Thailand? It’s one of the most populated regions in the planet with very high volumes of shipping and air traffic, and 20 country’s navies can’t find a trace of it?
Indian Ocean? Turned off civilian coms, took a deliberate unscheduled turn, passed through 4 IFR waypoints... and then just routinely crashed nbd?
Notice that the sources are anonymous and they use the word “suggests”.
The entire Gulf of Thailand is less than 250 feet deep...