If the plane managed to ditch in one piece and then sunk, it wouldn't leave a debris field.
If it flew west, it would be still in darkness when the fuel ran out, unlikely to get down in one piece, and if it did, it would mean it was survivable the pax and crew would get out. There are portable ELB's onboard in the emergency kits. Those ELB's are water activated, so even if they didn't leave the plane they would transmit, though probably wouldn't be heard.