How does Emily Pauline Johnson define "Who are we here" in The Lost Island?

In the short story "The Lost Island," Johnson draws a connection between the truth of who the Indians really are, or once were, and a lost island upon which, the old tillicum says, there is "something... that I want. I shall look for it until I die, for it is there."
The island seems to represent the endurance of a way of life which has been largely lost to the Indians in the story. The story opens with the "old tillicum" enumerating all the elements of the old way of life which have been lost to the coming of the white man: lands, game, religion, dress, and even language. As a reader, we can appreciate what the old man says about how the Indians are drawing away with each generation from the way they once were. However, in the myth of the lost island, the Indians cling tenuously to the idea that the way they once were, and who they truly are, still exists, but is no longer within reach—even the old man has reached "only the shadow" of it. In the context of the story, even the oldest of these Indians is only a "shadow" of what his ancestors were before.
The island represents the courage and strength of the Indian people. In the story the old tillicum tells, the great Indian medicine man begs,

Let not my strength die with me. Keep living for all time my courage, my bravery, my fearlessness. Keep them for my people that they may be strong enough to endure the white man's rule. Keep my strength living for them; hide it so that the Pale-face may never find or see it.

And, indeed, the island has been concealed from "the Pale-face." However, the melancholy implication of this story seems to be that, although the strength of the original Indians and their way of life endures, it is no longer within their reach because they have been so forced into the culture of the conquering white men. Not only is the strength of the Indians hidden from the white invaders, it is even, for the most part, hidden from the Indians themselves, who have "lost" so much of who they once were. The old tillicum tells this story so that his children will not forget the past, but that past, it seems, can never be recovered.