They do have sign in sheets at trailheads to Wilderness and stuff like that, and Yellowstone and Grand Teton require backcountry camping permits, but I am pretty sure the National Forest doesn't, or at least I have never bothered to get one. That may have been where you read it. Its just National Parks I am pretty sure. I think the rangers occasionally check the sign in sheets, but I think it is up to your family to notify search and rescue if you don't check in on time. My mom called search and rescue on me one time. It got late in the day and I hit a snow storm and just decided to hunker down for the night under a rock. I was pretty comfy and sound asleep when they found me, but pretty embarrassed.