Mending - sowing

I took a pair of trousers to be repaired and when I received the SMS from them to collect I went to collect only to be told that they do not have the trousers anymore as someone came in said they lost the receipt and alledgedly gave my cell number without the Pro Forma invoice which I have, .. Laundry Dynamics then gave them my trousers. The owner refuses to take any responsibility for this.