Augustine, arguing against the view that when Christ descended to Hell, he brought salvation (or preached for the first time) to those who died without having the opportunity to know Him, appears to argue that this view, or in general the view that those who die without faith in Christ may be united to him in death, would make faith in Christ useless or worse than useless:
Those who hold this opinion do not consider that the same excuse is available for all those who have, even after Christ’s resurrection, departed this life before the gospel came to them…. But if we accept this opinion, according to which we are warranted in supposing that men who did not believe while they were in life can in hell believe in Christ… [if] it be alleged that in hell those only believe to no purpose and in vain who refused to accept here on earth the gospel preached to them, but that believing will profit those who never despised a gospel which they never had it in their power to hear another still more absurd consequence is involved, namely, that forasmuch as all men shall certainly die, and ought to come to hell wholly free from the guilt of having despised the gospel; since otherwise it can be of no use to them to believe it when they come there, the gospel ought not to be preached on earth, a sentiment not less foolish than profane. (Augustine, Epistle 194, Ch. 4)
Again, arguing for the impossibility of salvation without faith and baptism, he says:
God is not so unjust as to defraud righteous persons of the reward of righteousness, [Augustine may be here speaking in the person of his opponent] because there has not been announced to them the mystery of Christ’s divinity and humanity, which was manifested in the flesh…. before the actual preaching of the gospel reaches the ends of all the earth… what must human nature do, or what has it done — for it had either not heard that all this was to take place, or has not yet learned that it was accomplished — but believe in God who made heaven and earth, by whom also it perceived by nature that it had been itself created, and lead a right life, and thus accomplish His will, uninstructed with any faith in the death and resurrection of Christ? Well, if this could have been done, or can still be done, then for my part I have to say what the apostle said in regard to the law: "Then Christ died in vain." … If, however, Christ did not die in vain, then human nature cannot by any means be justified and redeemed from God’s most righteous wrath — in a word, from punishment — except by faith and the sacrament of the blood of Christ. (Augustine, The Merits and Forgiveness of Sins, and On the Baptism of Infants, book 3, ch. 2)
I would like to set these texts in comparison with two statements by Cardinal Joseph Ratzinger:
What troubles us is no longer whether and how 'others' will be saved. Through our belief in divine mercy, we now know for certain that they can be saved; but how this can happen is something we trustfully leave to God…. To be a Christian does not mean… to find salvation placed more easily within one's grasp. But it does mean an invitation to greater generosity of heart, to volunteer the service which Jesus Christ gives to all men of all times. We could even say that to be a Christian means above all 'to be for others'… To secure the salvation of all men, the Church has no need to be exteriorly identified with all men. (Ratzinger, "The Church's Mission in the World," in Rethinking the Church, pp. 48, 52, 53, translated from La Fine della Chiesa come Società perfetta, 1968)
We cannot start to set limits on God’s behalf; the very heart of the faith has been lost to anyone who supposes that it is only worthwhile, if it is, so to say, made worthwhile by the damnation of others. Such a way of thinking, which finds the punishment of other people necessary, springs from not having inwardly accepted the faith; from loving only oneself and not God the Creator, to whom his creatures belong. That way of thinking would be like the attitude of those people who could not bear the workers who came last being paid a denarius like the rest; like the attitude of people who feel properly rewarded only if others have received less. This would be the attitude of the son who stayed at home, who could not bear the reconciling kindness of his father. It would be a hardening of our hearts, in which it would become clear that we were only looking out for ourselves and not looking for God; in which it would be clear that we did not love our faith, but merely bore it like a burden. . . . It is a basic element of the biblical message that the Lord died for all—being jealous of salvation is not Christian (Ratzinger, God Is Near Us:The Eucharist, the Heart of Life, trans. Henry Taylor [San Francisco: Ignatius Press, 2003], 35–36).
Cardinal Ratzinger surely does not intend to affirm that St. Augustine lost "the very heart of the faith", but may intend to make a criticism of certain elements in St. Augustine, and likely intends to reject a certain way of interpreting or using Augustine and his teachings on grace.