No, it's possible that invincible ignorance is a thing - especially if one is an indigenous Eskimo in subarctic Canada.
So tell me, why God would not let the lonely eunuch from the Bible perish in his "invincible ignorance" in the middle of Africa; but instead send Peter with the sole purpose of instructing him and water baptizing him?
If there is an example of a true invincible ignorance working, we find it in this lonely Ethiopian eunuch. Because he is sincere and truly seeking, God, Who searches all hearts and knows all dispositions, makes sure to send him a missionary in the middle of nowhere. A true, salvific invincible ignorance is that which is so strong that actually calls God to send someone to offer the tangible Sacraments to the poor, persistent soul who is calling, instead of letting him perish without that which is much necessary for salvation, according to what has been divinely revealed.