As is noted in the title of this post, this post is speculative, and there are certain strict parameters in which this idea of being saved without the gospel must fall into.
Someone can indeed be saved without hearing the gospel. However there are certain parameters within which that said person must fall.
If there is a man living out in the jungle, alone, all his family have died, he is old, none of his ancestors for hundreds or thousands of years have heard the gospel, so that he can not have any knowledge of it, than we must assume that God holds him innocent. He is innocent in a child like way. In the same way that a baby does not at first comprehend that it is wrong to bite.
If this man dies, without hearing the gospel, it is safe to assume, I think, that God will have mercy on him, because of his innocent ignorance.
The man never heard the gospel, has no way of hearing the gospel, thus the man is innocent.
This does not mean that one can somehow manage to “forget” the gospel and live life as they please with an assurance of salvation. Once the gospel is heard, the innocence passes and is gone forever.