My husband's ex-girlfriend left him a message, and I told him, but why didn't my husband return it?

Because he cares about you, he's afraid of your oversensitive, not that he doesn't want to go back. Men and women are different. Men have an advantage from the beginning. The so-called no loss is because he is a man, and he will not be too hostile (establish hostility) with a normal thinking because he is not good to anyone, especially his family and friends. Under normal circumstances, he will go back, because you know, so he won't go back, afraid of you. Mainly care about you, you have to understand him. What you do is up to you.