Never heard of a pot being used to ward off evil, but I have heard of shoes being hidden in hearths, and other spots in a house, and witch marks (scratchings) in buildings to ward off evil spirits.
1500 was about the time people started burying St. Joseph medals in their foundation. I wonder if they’ll find one? or maybe even a St. Benedict medal? Could that have been what was in the pot?
I guess the pot didn’t work.