An engine failure at night can emit a huge trail of sparks. Quite possibly one that is visible for miles. Completely plausible that this rig worker did see something. But no wreckage below.
Aircraft then turns westwards towards the wrong TRN VOR (as outlined by tarzanboy, copied below) descends
by 10,000 feet -a figure mentioned by the Malaysians (but in meters). That would roughly correlate to drift down to the 777 OEI cruise?
Heads to wrong VOR, overrun with other problems (fumes/smoke) aircraft keeps on trucking westwards.
What if MH370 wanted to perform an emergency landing for whatever reason. Close to IGARI point the crew entered a possible airport to land in their FMS which could be VVCT CAN THO with VOR "TRN", because this one has a 3000m runway which is close to the intended route ahead. But, there is another "TRN" VOR closer by, guess where: TRANG VOR close to the Andaman sea. The crew under severe stress executes the top TRN (closest by) in the FMS and the plane turns immediately to that point. Could this explain the hard left turn after IGARI point towards the Andaman sea?