I have always believed that Casey was afraid she might possibly marry him in spite of himself if she were in his immediate neighborhood long enough.
They made themselves each a small pack of food and what was more vital, water, and went their different ways.

Hahnaga struck off to the west, to her brother at the end of Forty-Mile Canyon.

At least, that was where she said her brother mostly camped.

Casey retraced his steps for the second time to the camp of the tenderfeet.

Loco Canyon, Casey calls the place, claiming it by right of discovery.
Now I don't see, and possibly you won't see, either, what the devil's lantern had to do with Casey's bad luck.