it really depends on the DOH regs in that town/state regarding food handling and allergies. It sounds like a small town so I wouldn't be surprised if they had next to no regulations on the books regarding these types of incidents.

It sounds like the diner did everything in their power to accommodate the allergy including having the cook clean the grill prior. The kid probably was being a kid forgetting momentarily the severity of his allergy just so he could be normal like his friends. A very unfortunate situation all around for everyone.