When Armand finds her, why do you think the author chose to have it happen at the same location?

Désirée's location at the stone pillar is symbolic. She was first found at this site when she was a baby. Thus, we can infer that the author intended to parallel these two events when the narrator reminds us that this is the same location where Désirée was discovered by the Valmondés. As a symbol, the location serves as a place of transition. It is the place she finds her first home, as well as the place that she finds her second.