That is an allegation. That is what they say concerning Ishmael. Some people have said that the Quran doesn't name the son of Abraham specifically and that early Muslim interpreters were divided over whether it was referring to Isaac or Ishmael. Technically, some of the descendants of Ishmael may have became Muslims as early as around 700 A.D. but not before that. In other words, Islam was not around before that century.
RE: Proof that they have located Noah's Ark on Mount Arrarat, and it is more technically advanced that we were told!