A left handed piano in an abandoned house in a devastated village in the middle of the war? Now that's what I call luck. 
um, that's not from the abandoned house.
that scene is from the radio station when he plays the nocturno...and yes, it's mirrored because the black keys are not arranged as 3-2-3... but 2-3-2 starting from the left to the right....as we all know

And I doubt it that left hand pianos could be used in a film.I mean, most of the greatest pianist play,played on "normal" pianos...
And in the "abandoned house in a devastated village" he plays the ballade in g-minor...
How can he be playing in a devastated house in the middle of the war wearing a fancy suit?
Oh come on.