If the seat was occupied, it is state law in Illinois that the insurance company must replace the car seat. this will only apply to full coverage insurance last time I checked. Regardless of the law, if the manufacturer says it must be replaced, then it must be replaced. Have the manufacturer get you a letter to give to the insurance company. Also, you could try telling the insurance company that you want a letter from them stating they will be held responsible for anything that happens to your child while in the seat in a future accident if the seat fails, if they won't replace it. It has worked for many in the past.