I don't know what happened to Serenity. I do know this entire case was off to a very wrong start and findings show this, whether intentionally, negligently or otherwise, much is in a report and it is a published "fact".
Other than that, there are few facts that we ourselves have any evidence of.
There are three likely possibilities imo, with possible variations of each.
Something happened at the home. (Whether accidentally or criminally as possible variations)
Someone abducted her whether stranger or someone known from the roadway. (Or from the home, parking lot, etc. as variations)
She ran into the woods and died there. (Variations, found a farm/outbuilding and died there, etc.)
Thanks to the wrong start, we may never know imo. Maybe we would not anyhow hard to say, but we will likely never know.
Her body may be found one day, the odds of it telling anyone anything are slim. If they do find her in the woods, to me it will not eliminate other possibilities at this point unless something very definitive shows otherwise when found.
I would love to believe that she is being held by some good hearted person but the likelihood of that seems pretty slim to none.
All jmo and yet pretty much fact imo. Not a slam at the home, parents or anyone, just fact and possibilities.
Feeling a bit negative about it all and with no answers that will ever come which is how it is looking and imo, always has looked. I guess we can all be left to what we feel the most likely scenario is.
I still pray and hope Serenity is found. She has turned into one unforgettable child for me, even though I realize we do not "know" her.