RevRandy.... I don't think that you followed Defender's train of thought. I understand him to be saying...... what about the person who made a conscious decision to walk away. How much time and energy should a minister (or even a layperson) be expected to put into going out into highways and byways to compel that one to come back. The Bible says the prodigal "came to himself" and made the same conscious decision to come back to the Father's House.
The coin.... those are the people who have never heard and we try to reach by many methods.... the sheep - was wounded or "strayed" for any number of reasons and we make every effort to restore ..... the prodigal - he told his father, "give me what's mine - I'm leaving" It was a conscious choice that caused him to wind up in the pig pen - and he made a conscious choice to return.
So to me, the question that was raised is where does the responsibility end to bring the prodigal home? - or does it ever end? The father waited until the prodigal came home - he didn't go to the pigpen to get him...
This is just my intrepretation.....