Randy,
Was the flatcar you mentioned presumed to have gone down with the engine? Is it clearly known whether the locomotive alone went into the river, or whether other rolling stock went in as well?
What does this site look like today? I would imagine the river is still in the same place, but I wonder if it is lined with houses by now or if it is just a spot in the woods. Even if the locomotive was recovered, there is a high probability that some smaller pieces such as oil cups might have broken off and been lost. It would be interesting to look at the river during low water to see if any pieces might still be there and showing. Rivers have a way of hiding things for a while and then revealing them later. A metal detector might find some fragments. A magnetometer would find the flatcar if it is buried or submerged.
RK