The No. 3 (C-minor) etude from Rachmaninoff’s first set of Études-Tableaux, Op. 33 was omitted from the original publication and released posthumously. I haven’t read anything that explains why, but it probably has something to do with one of its melodies making an appearance in his fourth piano concerto, written some fifteen years later. 
I guess it’s only expected that, as a composer, you would eventually come to realize that a particular figure might shine a little brighter in a different setting.
What a melody…
Etude performed by Rustem Hayroudinoff (Chandos). Concerto by Leif Ove Andsnes (EMI Classics).