Dirty Mop strand found in food

I found a dirty mop strand in my food. The manager had the nerve to lie and say it was a new mop head and offered a free drink, I am even more upset today because it had time to sink in, this man **** to my face knowing good and well that we both knew that was a USED, DIRTY mop strand. It’s the next day and I have food poisoning from their food.