McDonald's

Hello, I am quite disappointed with my last visit to mcdonald's because I was served meat as I am a vegetarian. I understand that it was a mistake but there was not even an option on the menu that said it came with meat. Whenever I go to mcdonalds, I always get the same thing and it has never came with meat. I did not think to check because as I said before, this is a common food for me and it never comes with any meat. I am not sure what needs to be done but I think they should be more careful with orders that are supposed to be meatless. Thank You.