This is a big puzzle. Some believe that there must be a remnant hierarchy left somewhere in the world. Others believe that canonical mission is not necessary in a time of necessity, and so those priests ordained and bishops consecrated without canonical mission are the hierarchy, albeit imperfectly constituted. The solution is lies in the understanding that the Church has not defected, because only the See of Saint Peter is said to be indefectible, which See has been vacant for over half a century. For those who insist that there must be priests in the world, read this article.