I remember reading somewhere as a kid , I think it was the ESB storybook , that Dagobah did not appear on any star charts or maps and that the Force guided Luke there . Based on Luke saying something was familiar about the place in the movie , I assumed we would see him taken there for a brief time as a baby in the prequels ,but still thought Yoda just went into exile there like Kenobi did on Tatooine ,and that they both never always lived in those places . I do remember though ,that there was a piece of art that was published in the early to mid 90s ,that depicted a young Yoda being trained by a serpent like alien on Dagobah . This was before the prequels were being made ,so apparently ,there were some who thought what the op mused about .