Artists, have you ever created something you thought was original, but it turned out that it wasn't?

Sure, all art is derivative to some degree. On one end of the spectrum, most pop songs follow a strict formula and 4 chord progression (Axis of Awesome’s “4 Chords”). But even most independent music is built upon a well-defined foundation, that is rich with cultural references (musically).

There are times when a musician is sued for completely ripping off a song. In some cases, it seems entirely possible that two musicians could come up with a very similar song independently, as music’s influences within a culture progress in rather conservative and sometimes predictable ways. Of course, there are other times when it most likely that one artist heard the song, liked it , and either copied it or forgot s/he had heard it and thought it was his/her own creation.

A few years ago, I was playing a chord progression and building up some changes into the chords and strumming to hint at a melody. It was a relaxing little thing, and I built up drums and bass in my mind, and fully built how the vocals would go. After months of occasionally returning to “my” song, I was completely shocked to hear it play out of my MP3 player. It was a song I had heard (multiple times, years ago) and had completely forgot. The melody and every little detail were exactly what I had imagined that I had created. Yet, I had not. Creation in this case was remembering.

Have you ever created something in this way? A painting, sculpture, poem, song, or story?