I would first ask … which way was any air flow moving? Not just right at the moment of the search, but all throughout the day while the odor was cooking. It sounds like it MIGHT be that the odor was moving from it’s hide 2′ up on the stone column ACROSS to the plaque, where it was likely pooling. It could be that there was not enough odor available to her on the hide side of the column to get her attention. Odor doesn’t sit still much, and it doesn’t necessarily drop straight down.
If Scout paid the most attention to the back/sides of the column, it’s probable that is where she felt the odor was strongest.