One thought has occurred to me - after 1958 the builder decided that the car was no longer competitive, although it was entered for the 1959 race, and the entry was declined by the ACO. It had raced in various forms since 1953.
In 1960 the ACO introduced new regulations for prototype cars, trying to bring them more in line with the production GT cars, and one of the new rules was that the windscreen had to be a minimum height. I wonder whether the car was redesigned with the possibility of an entry in the 1960 race?