Here it is at last ladies and gentlemen. The long awaited Italian augmented sixth chord, finally found in Wolfgang Amadeus Mozart's Piano Sonata in D Major, K. 284 the third movement, the seventh variation.
The first clue I found was that this section was written in the parallel minor key of the original theme, and every other variation thus far. This was immediately where I began my search knowing that most often than not, augmented chords are found in minor keys.
This variation is the only one in a minor key making it very special. There are actually two separate Italian augmented sixth chords. The first appears in the third full measure, beat four, before the first repeat sign, and in the second to last measure before the second repeat signs. Both of these chords, by definition, feel and sound like dominate seventh chords but with a funky resolution. This being said these chords give this variation sudden, unexpected feelings of being Major, perhaps someone almost let the sunshine in.