Typical naval air search radar operates out to approx 450km and to a height in excess of 150,000ft.
There may well have been many warships out there but the radar operators are trained to take notice of a contact if it threatens the ship, ie... Flies towards it. Single contacts at high altitude on a constant heading are usually deemed friendly and ignored.
Is this data saved at all ?
Reviewing it may reveal something?
That's of course if there were any Naval ships in the area at all.
They are activated by a g-switch which is one of the reasons why they are so unreliable.
I know that ocean going EPIRB's are available that activate on contact with water. Surely that could be built in to Aircraft models.