The couple may have also used a gift card or store credit, which isn't a coupon, but the cashier may have misstated it a bit for effect. We bought a BBQ grill from the Home Depot for "free" because it was on sale, we had two coupons that were allowed, and we had several HD gift cards. The cashier said "Wow - a free grill!" because we didn't have to give her cash or a credit card, but technically, we paid more than half with the gift cards. (Which were from credit card points, but the cashier didn't know that.)
