Waste of time and petrol!

Yesterday I went for some groceries. I am breastfeeding and need to drink lactose free milk. I purchased 6 with my other items, paid for my items and thanked the packer for packing the trolley. I got home to find 3 milk cartons missing! When I went back to Pnp I was simply told it was a mistake! They gave me the milk to replace, but I am angry that I had wasted a full trip there and back for the milk that wasn’t packed in my trolley of other goods in the first place! Petrol is expensive, it is lockdown and I am without work, I cannot understand how only 3 milk cartons were forgotten to get packed when I had a trolley of items??? For mistakes such as these there should be some compensation, not simply a “sorry it was a mistake” and I had to waste time and petrol going back and forth for the items I paid for in the beginning.