Apologies if I've got this wrong and I've completely misunderstood, but where does loading/unloading come into this?
The OP has said from the outset:
"... Items included 6 bags of 20 kg special type of rice and 5 bags of 10kg Ground rice. I had to park as close as possible to the shop for easy access because of the weight, bulkiness and the number of items to be purchased and load into my car.
We have previously purchased these items from them that store. None was available on the shop floor. The shop assistant had to go into their stock room to check if they had any at the back.
They didn’t have any in stock but they can order it in for me. This process took a while about 5-6 mins. Came back to my car to find a PCN." [My bold for emphasis]
I understand that to mean the the OP made a speculative journey to the cash and carry to purchase rice that they had not pre-ordered. When they got there the cash and carry didn't have what the OP wanted, so the store ordered it in for her, and she left empty-handed.
That isn't loading, is it? Or have I completely misunderstood?