Lack of the 
returning f is most probably Chopin's oversight here. The composer's concentration may have decreased when, after the chromatised bar 17, he reached the diatonic progression in the main key. In any case, the accidental added in a proofreading of FE (→GE,EE) must be considered to be binding. Similarly in bar 58.
Compare the passage in the sources »
category imprint: Interpretations within context; Differences between sources
issues: Omissions to cancel alteration, Errors of A, Authentic corrections of FE
notation: Pitch
