Unless you were there with him and his dad's friend, you'd have no way of confirming that he wasn't lying. Or that he hadn't hallucinated. Or that you hadn't

Unless you were there with him and his dad's friend, you'd have no way of confirming that he wasn't lying. Or that he hadn't hallucinated. Or that you hadn't imagined or dreamed being there with him. Or that the universe wasn't created moments ago, and all of these memories are false.