I'm a vegetarian and they gave me a beef patty

I ordered a vegetarian Mushroom swizz takeaway burger. When I got home I found a beef patty instead of my vegetarian one. I'm not only disappointed, but if I have been a vegetarian for over 19years and I had to deal with finding a meaty patty in my food after a long day of work. Unfortunately I can't return it since it was late at night and the store would have been closed at the time of arrival.

I'd appreciate a refund to be honest.