Tigerfish, do you have any idea how hard it would be to successfully ditch a plane in an ocean? Add in other factors beyond just ditching as well. Sea conditions, time of day (or night), weather, instrument error, Mental state, pilots experience, fuel...the list goes on and on. The chances of her ditching the plane with no damage is microscopic.
In all likelihood, if she ditched in the ocean it was probably unsuccessful. The plane probably broke up and sank in short order. If they were injured in the crash, they probably went down with it.
If they were able to get out of the plane and get a raft set up before the plane sank then maybe they survived for what...a week? 3 at most? That's assuming they didn't get injured during the ditching.
As far as seeing a submerged airplane, if it was in water, even in one piece it'd be hard, if not impossible to spot depending on the seabed and depth. Even in shallow water (And I mean shallow. If it's 15ft down I'd be surprised if you could see it from the surface), when it hits the seabed its going to kick up sand and dirt that will settle on the horizontal surfaces, killing the reflectivity.
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