You absolutely should go down there and have them read the necropsy so that they can alert other pet owners that had their pets spayed that day. And hopefully, they will learn from this and be more diligent in their work. It is unacceptable for that to happen in a professional practice, but accidents do happen, people are forgetful and it is just really upsetting and awful that it had to happen to your baby. I really hope you go there and let them know what exactly has happened and stress that it was THEIR fault. I would also assure them that you will never be taking another pet to them for any sort of services. I know I wouldn't.
I do not think we can sue them as I am pretty sure we signed a waver. The spayed so many other pets that day. I am worried that it is not only my pet that was hurt. I cannot even express in words how much it hurts to know that they killed my baby and they might have killed others.