Piece of glass in meal

We went in to the restaurant for my cousin's birthday and we had ordered our food. As I was eating my meal, I bit into the something sharp. When I felt it around my mouth, my mouth was stinging. I took it out to see what it was and it was a piece of glass! To my dismay, I had asked for the manager and the manager came over to our table. I showed her the piece of glass and she replied to my complaint by claiming that it was probably "rock salt"! Salt generally is white and this was a huge piece of green glass! I told her I didn't appreciate her not taking me getting hurt in my mouth seriously and questioning my intelligence. She then took the glass and left without any other response. A few moments later another manager came and said that he would comp my bill for 50% and that he was sorry about the piece of glass. He told me "it happens from time to time." I told him that wouldn't be the last time they heard from me and he responded "I'm sorry that you feel that way." As I left with pain in my mouth and angry as ever, I felt that they never took the necessary actions to solve the matter, but instead tried to get rid of the problem by cutting the bill by 50%! Not interested at all in me getting hurt by the glass.