Well, I thought about it before I used it, and it seems to me that まだ帰らなかった would show that someone hasn't returned home yet and implies that they haven't left for home yet. On the other hand, まだ帰っていない would mean that they haven't reached home yet. That is, they could still be on their way, or they could have not left yet. And まだ帰ってきてません would mean that they haven't come home yet, i.e. you are where they are going. I meant it to mean that someone has not left yet and you are where they are leaving, and that there is no way to know whether they have arrived yet. Now, I'm not sure whether or not native Japanese speakers make this distinction, but it seems at the very least to be logical to me. I could have been going out on too much of a limb here, but I guess we'll have to wait and see.