I'm aware of the passage from Moonlight Sonata 3rd movement. Are they others besides that?
While cleaning out my studio the other day I found a book I didn't know I had, "Chopin" by Arthur Hedley, a nice concise 222 pp. and the best short bio on him I've ever read; it focuses on the music, not his personal life. At any rate on p.170 it says..
"Early in 1834 Chopin sent his sister an album containing the Nocturnes op.15, which Schlesinger had just published. In it was also a copy of Moscheles' Impromptu in Eb op.89, which had appeared simeltaneously with the Nocturnes. A glance at Moscheles' piece shows whence Chopin derived the idea for the work issued after his death as a
Fantaisie-Impromptu, and explains why the composer did not publish it, in spite of it's superiority over Moscheles' commonplace work: the plagiarism would have been too obvious. Here is Moscheles: (there is a four measure 4/4 RH excerpt in the book; all notes are 16ths except the last of the first three bars which is an 8th. The pattern in the last measure is two 16ths one 8th )
(first two bars) Eb D Eb D /Eb F G Ab /Bb G Ab A /Bb Eb G/ (2nd bar repeats the 1st exactly)/
(bar three) Ab(up a seventh) G F Eb /D Db C B /Bb A Ab F /D F Bb/
(bar four) D F Cb /D F Bb /D F Cb /D F Bb/
Well writing that out was annoying!

Maybe it's time to install the scanning hardware...

Anyway if you try this out you will hear a happy perky Fantaisie-Impromptu... I wouldn't have published FI either; wonder what the whole Moscheles Impromptu sounds like, is there a mirror of Chopin's middle section? In this case Moscheles' would have to be in eb minor. Perhaps someone has the music in PDF and can post it!