The character has a health bar and radiation lowers it in one end. Perhaps failure to roleplay could lower it in the other end?

Seems like the game is missing a meter to display failure to roleplay the imagined need to find the lost son. It is kind of like the difference between main and side quest in an open world game. And the meter is missing because pursuing other quests or radio emergencies is a delay in finding the lost son - a roleplay failure!

For example if the game told your character needs to pee, and instead of doing that he goes wandering about, because hey it's an open world out there, there's no display of urge. And according to the game the character is a father or mother with an urge to find the lost son ...