Unexceptable bussiness practice

I need to warn customers. Not sure if all stores has this policy but the store in Jeffreys Bay does have a policy of keeping a receipt and paperwork for items to be delivered or collected. I bought 2 garage doors for collection and paid cash and when asked for the slip was told it remained with them until collection. Now they cant find my purchase for over R3400 and I have only my daughters and my word on the fact that we did go there to do the payment for the doors . My money went into someones pocket and Im not able to see cashiers transactions for these amounts