Lice Eggs after treatment?

My daughter came home at the end of April with lice and was sent home. Our school has a nit free policy so I treated her and it took me two days to get everything out. I also treated my hair, washed everything in the house and checked my other children. On May 1st after two treatments and a check by school nurse she was allowed back to school. I might also add that the nurse checked my hair as well and said she found a couple of eggs and pulled them out and said I was good to go. I did one more treatment to be on the safe side. It is now June 18th and I went in to get my hair cut and the lady said she found 3 eggs in my hair and I had to leave. That alone was totally embarrassing, but I understand from a business stand point. She was very upset, said she would have to close her shop for the day to clean. I came home in tears, checked all my kids and had them check my hair as well and couldn't find anything. I have hair that is very, very long and not easy to look through. I wonder if maybe I didn't miss something and thats what she saw, but its been more then a month wouldn't I have more eggs?? The nurse told me the shampoo killed the eggs as well as live bugs, the box said it also kills the eggs, I did three treatments, used hair dryer every day to help kill eggs with heat and still this happened. Looking for advice from people who have gone through something similar themselves. Thank you for your help.