I think it probably went further than you searched - around 4 km. If you extrapolate the battery level at the final rate of depletion to the autoland level at that altitude, and then estimate aircraft position based on drift speed in RTH to that time, plus around 30 s to descend from 80 m, you get the following:
View attachment 39536
That suggests it should have landed at around 9985 m from the home point. Extending the final track on the map to that distance gives:
View attachment 39537
View attachment 39538
With a guess of ± 3° uncertainty in the heading for that period of drift, we get a lateral uncertainty at 4 km of around 400 m, and that's probably not a bad uncertainty estimate on distance either. The resulting area estimate is depicted by the yellow circle. That's where I would look.