False black Friday advertising?

Westpack Montana had notices in the shop on Black Friday that read: "20% off all store items" But no items were discounted when we paid for our shopping. When we enquired, they said the 20 % was already reduced on the racks. I have not seen any discounted price on the racks and seriously doubts that Westpack had ALL items in the store marked down by 20% only to put up the normal prices last night to be in order for today??