I am trying to solve a problem, and I solved it based on someone's article's results. I have written a manuscript and sent it to a journal.
While reading that article again, I found out that my manuscript's main contribution has been already proven in it, but I never realized that in the first place.
To make things complicated, if the results there were combined with other results in another article (by the same author), one can fully solve the problem. However the author never made a claim about this.
Furthermore, my work is slightly different from that author's work (although his work is more direct I think). In this situation, does my work count as having independently solved the problem?