At around the same time Annie Proulx published “The Blood Bay”, an episode of Six Feet Under saw Claire in big trouble for stealing a severed foot from her family’s funeral business and taking it with her to school. That episode, like this story, was darkly funny and made use of someone’s severed foot.
It was inevitable that a TV series called something about feet would have to at one point make use of an actual foot.
While this is icky, North Americans haven’t been so squeamish about carrying around rabbits’ feet for good luck. Larry McMurtry writes of that practice in his cowboy novels. (Only the left hind foot is lucky.)
Severed human hands have a stronger history in folklore than severed feet. Characters with severed hands tend to be either victims, or monster-like villains. For more on that see Severed Hands as Symbols of Humanity in Legend and Popular Narrative by Scott White. The severed, walking hand also makes for a memorable horror scene.