You don't need to worry too much after you told him your concern

That manager will learn his lesson later. He might need a lesson since he hasn't got one. So, he gets a chance to grow up. If the bug shows up, CEO or customers will make him to respond to the bug fix. You will still get a chance to fix the bug after customers complain. You don't lose anything, and the manager will respect you, and still keep good relationship with you. Good luck!