Zero cases of something are not exceptions- John Martigioni
In reality there are no known cases of persons saved in invincible ignorance and the baptism of desire.
In principle we accept the possibilty of a person being saved in invincible ignorance and the baptism of desire and these cases would be known, visible, only to God.
Every one needs to be a visible member of the Catholic Church and there are no known exceptions.
If there are no known exceptions there are no exceptions to the dogma.
There are no known exceptions to every one needing to be a visible member of the Church for salvation, to go to Heaven and avoid Hell. -Lionel Andrades