I had gastric byp done, at the time I had gallstones that the surgeon was supposed to?

remove at the time of the operation--he didnt do it, he told me husband in the recovery room that he must not have read the report clear through so i had to have another surgery to have the gallbladder removed, is this a malpractice issue? I am just curious. or do you think it was just a stupid oversight by the doctor?