where did sauls sister disappear to? Why is this event so important in his life?

Naomi tells Saul and Benjamin about how, one day, the white man, or “Zhaunagush,” came to their community and abducted Rachel, taking her away by boat. She would have been taken to resedential school. This affected Saul greatly: he lost his sister to the white world. Saul will lose himself to the white world.