I want to know the most natural expression. please help me. Context is : If my son went out and he didn't come back home yet. He had told me he will be home by 10. Now it's 12. I've started to worry him. I want to know why he didn't come back. It may be because he forgot time. I'm gonna text him to ask 'why'.
In this situation, should I say "why don't you come back?" I think it sound weird...