Even if the Mass and most sacraments and the hierarchy disappear, we have Baptism, a record of infallible de fide teachings from unquestionably valid councils and popes, the writings of the saints, the Clementine Vulgate and Doway-Rhemes Bibles, and the Rosary and Brown Scapular and the Act of Contrition. The True Church is indefectible. Some will argue that under those circuмstances it would lose its mark of visibility, but I'm not so sure.