Sarcastic cashier

I went to Markam Cavendish for the sole reason of returning a Father's Day gift which was the incorrect size. I had already purchased a new one at one of the other stores but did not have the first jacket with me on that day. Unfortunately the receipt is no where to be found but having an account I thought it would be okay. The store was quite busy and I felt bad because I know they hate doing returns and this cashier tells me that considering I don't have the receipt with me it will take ages to get it and call the branch I bought it from etc etc. I then reply so what should I then do because this is the only way I can return it. I admit I was a bit frustrated but not rude nor did I raise my voice I was completely calm. He then tells me yes well you don't even have the receipt in the most sarcastic and unhelpful tone. He really spoilt my day to be honest, I have never really been given terrible service at the store but this experience has left me not wanting to go back in there. My sister was so appalled that she wanted to make a scene right there but the employees where all about moving on as fast as possible. I doubt I will want to go back there again.