There is no salvation apart from faith in Christ. But what about those who haven't heard of Christ? A standard story is that they can have a spiritual relationship with Christ even though they do not know that they are having a relationship with Christ. They can be "anonymous Christians."
But faith is supposed to be an interpersonal relationship. The kind of hidden mysterious relationship that falls under the head of anonymous Christianity seems to fall short of the best kind of interpersonality, and seems not to be very incarnational in character. Now, there is nothing wrong with saying that although it falls short of the best kind of interpersonality, it is sufficient as faith. But I want to explore a dimension that gives more of an interpersonal and incarnational aspect to being an anonymous Christian.
Suppose that our anonymous Christian is blessed by being in a community with other anonymous Christians. They are all, unbeknonwst to themselves, animated by the grace of Christ. They are all, unbeknownst to themselves, members of the body of Christ. Thus in relating to one another they are relating to Christ. But their relations to one another do have the right kind of interpersonality and incarnational character. The presence of Christ through other anonymous Christians in their community—maybe even everyone in the community is an anonymous Christian—make their implicit faith in and love of Christ much more of an interpersonal relation than it would otherwise be. And of course in this regard they are not that different from explicit Christians, since so much of what we know of Christ is based on what we know of people whose lives are made radiant by Christ's grace.