Margarete Heymann was a gifted ceramicist who had a falling out with the director of the Bauhaus school and now is largely ignored in the influential 20th century design school’s “official’' history. Her work was original, functional, very beautiful and remarkably advanced for its time. The reasons for her obscurity tell us as much about why some people are cast as winners — and others as losers — in design history, as about the Bauhaus and Ms. Heymann herself.