I agree, the torque settings would have been inferred from the position of components within the engines, rather than cockpit instruments. The position of fuel feed and oil feed valves, or witness marks, would provide an approximate indication of the power settings on the engines.
If engine four separated on or shortly after contact with the top of the embankment and then tumbled some distance to a final resting position, the disruption and damage to the engine might cause several sets of witness marks which would be difficult or impossible to accurately decode.