The boy specifically stated that he wanted to follow the creek potentially to a lake or other civilization. There really isn’t a much better plan if you are going to be moving than to follow the water.
I'm sure that's sound advice in some terrain. But in others, notably in some mountainous terrain, following a watercourse often leads you into an increasinly steep, dangerous, narrow, thicket-choked ravine, where you are more likely to get hurt and less likely to be spotted by searhers. There are few hard and fast rules.