My dentist submitted a bill to my insurance company for crown lengthening surgery. He never mentioned this to me while he was doing the root canal and casting for the crown, all done same day. Shouldn't I know if I had this surgery, Pain stitches etc. From the pictures on the internet it appears to cause damage to the gum.

I would think you would have had some discomfort. I'd notify the insurance company. Dentists are not supposed to do any treatment unless they inform and get consent from the patient. If you were not informed and didn't give consent, I'd consider it not done!