I keep thinking back to when I was a kid, and enjoyed playing in the woods behind our house. Immediately behind our house, there was an old, very overgrown garden plot full of briars. One day I noticed what seemed to be a trail going through the briars, making a low tunnel of sorts. Being curious, I squatted down and went into the tunnel. The trail wound around, went down a short but steep hill, then opened up into a small opening surrounded by trees. It amazed me. I'd found my own little secret spot in the world. In reality, the area was actually surrounded by houses that were behind the trees, and my parents knew exactly where I was, but I enjoyed having that quiet little spot all to myself. I think part of it was knowing that my parents couldn't have crawled through that briar tunnel. It was too low and narrow for adults. That spot was ALL MINE.
I pretty much stayed "in trouble" when I was a kid (I had very strong opinions and didn't hesitate to voice them! LOL!), and my sister and I constantly butted heads, so that spot became my own little "escape".
From the video of her dancing in the rain, Summer reminds me a lot of myself when I was that age. Tomboy, free-spirited, curious, nature-loving, didn't care about being muddy or wet, etc.
I wonder if Summer found a "secret" place like I did, for enjoyment and/or perhaps as a quiet spot to get away from sibling squabbles, etc. If so, her parents may not have even known about it, especially if Summer had recently discovered it.
What if she went there, got distracted by a pretty rock or an animal, or perhaps even fell asleep, then before she realized it, it got dark? Would she stay put, or would she try to go home? Me, at that age, I'd probably try to go home in the dark, knowing that the longer I was gone, the more upset my parents would be with me for staying out so late (understandably). I wouldn't have realized it would be safer for me to stay put until morning.
The terrain here (Chattanooga area) isn't quite as rugged as it appears to be in her area, but even here, there are places where it would be soooo easy to make a mis-step or trip over a root or rock, and slide down a hill into the underbrush. If you were injured to the point where you couldn't call out, or if you were afraid to call out, it would make it difficult for searchers to find you because of the underbrush.
There are also holes, caves, deep ditches, rocky/root-y creeks, etc. ... all of which could potentially make a person (especially a small child) difficult to find.
I'm still hoping for a miracle, but it's sure not looking good.