In the 2007 local adventure story I posted a while back and will repost again, the writer mentions that the trail down to the river accommodates 4-wheel drive vehicles. He encounters two men camping at the river, who drive up the trail in their Jeep. I would assume LE would see tracks if a vehicle had travelled the path recently. But that's one scenario I haven't heard discussed, and it would be interesting to ask LE that question. Imagine if nefarious individuals encountered the family on the way down, and like
@Pumphouse363 has written, they feared going up the same way, or individuals drove the family down to the river against their will and dropped them off. I realize this is grasping at straws but had to toss it out. Perhaps someone here knows if vehicles are still allowed on the HC and SC trails. IMO the family died from heat-exhaustion, but it's hard to imagine why they set forth on a trail for a Sunday outing that locals will not set foot on in July and August.