You are not alone.
Many of us have done it.
You're in one room. A member of your family is another. And you're having a conversation.
You are speaking up, so you can be heard. But after a bit, you realize that you have been doing all the talking. So you go to the room where you thought the person to whom you were speaking was. Only then do you discover that he or she left some time ago to go to the basement or wherever.
They say it's important to know your audience. But perhaps equally important is knowing exactly where your audience is.