Vomit in my food

Today, 04 Feb 2018. I went to this particular KFC and ordered a Hawaii burger but the STHEMBISO the cashier got the order wrong. When I received my burger I realized that it was the wrong order and went back and told him what had happened. He gave me attitude stating that this is what I ordered. After some time of convincing he ended up taking the tower burger to change. He took a good 20minutes with my food just replacing a hash brown with a pine apple. When I got my burger back I sat down and had a bite, only to have a horrible taste of vomit in my food. STHEMBISO added extra sauce to cover what he had done and when I confronted him, he just struggled his shoulders and said he doesn't know.