Here was the Facebook post of Catholic apologist Taylor D Barrett on whether salvation outside the church exists or not. The book he is referring to is Salvation Outside the Church? Tracing the History of the Catholic Response written by Francis A. Sullivan:

Gavin Ortlund mentioned this book in a video he did a couple days ago. Which is funny because I ordered it a month ago and have made a couple posts about it over the past couple weeks. I actually received a signed copy which is cool. I’m interested to see more on this subject as the conversation continues. So far I think the evidence is leaning in the direction of a real contradiction between the medieval and contemporary doctrines. Catholic apologist Dave Armstrong has argued the validity of Orthodox sacraments proves non-Catholic salvation, but this is obviously false since the medieval doctrine, while affirming their validity outside the Church, denied their efficacy outside the Church. Others have tried to emphasize the ancient doctrine of ignorance, as Joe Heschmeyer has in the past, but the medieval Church only allowed ignorance to mitigate culpability for not having explicit faith – it didn’t allow for it to result in the reaping of the benefits thereof. All evidence indicates the medieval Church believed that only explicit Catholic faith saved, and that all non-Catholics, even if they were baptized validly and gave their life as martyrs for Christ, were damned.