They can't be saved by their own religion. Their religion is a false one and has false understandings and a false God. They can be saved if the are invinciblely ignorant of the Truth and they naturally follow all the rules set on their hearts by God.
This means that if this Muslim person was exposed to Catholicism they would convert immediately.
This is how I understand it. I hope I understood it correctly.
No ... and this is the subjectivist Pelagian naturalistic poison that has infected nearly the entire world.
1) Ignorance cannot be salvific, merely exculpatory.
2) One is not saved merely by not having committed actual sin (that's Pelagian heresy in a nutshell).
3) Observance of the natural law cannot overcome Original Sin.
In order to be saved, one must have supernatural faith and supernatural charity, but following the natural law is ... merely natural virtue, or natural lack of acctual sin.
According to the Athanasian Creed, all the Doctors of the Church and several decision of the Holy Office, explicit faith in the Holy Trinity and tthe Incarnation are necessary for salvation ... and infidels canont be saved.
Where do the Sacraments fit into your theory? Council of Trent taught dogmatically that the Sacraments are necessary for salvation, with the Sacrament of Baptism being absolutely necessary by necessity of means for salvation. To deny this is heresy. Yet 98% of Trads deny it openly and even condemn the opposite as being Feeneyite "heresy".
So not only do we have Anonymous Christians, Anonymous Catholics, but we have Anonymous Baptism.