LW needs to evaluate both relationships. She seems so sure that nothing happened and that it is fine yet wrote to an advice column. It is not like husband hid anything. He did not say anything until prompted because he did not think it was something he needed to say anything about. I know plenty of married friends who would not mind such things and others who might be a bit more ruffled. tl;dr I think LW needs to look more at herself than those around her in this instance.