@LauraAnne, I agree that this is a very real possibility. But my concern is also that KR could be with her car parked somewhere - in the woods or among human structures and parking lots.
At 16, I doubt KR had much experience with using alcohol, pot, cocaine, narcotics, and / or hallucinogens. Those of us who indulged in our past, learned from years of trial and error what amounts we could tolerate, what we could mix and in what order, etc.
My fear is KR started driving somewhere - an after party? to Reno? to home? and after a bit realized she was feeling ill, woozy, confused, scared, and not able to process what was happening to her. In that state she'd possibly want to find a place to 'hide' in her car and rest or sleep it off before she continued or had to interact with another human.
From experience I know that many of the substances KR may have ingested that night have a delayed impact on your body and mind. Perhaps in this hypothetical scenario, KR parked somewhere, felt even sicker or mentally confused and eventually passed out. Sadly, with the right dose or right mix of some of those substances (e.g. alcohol and narcotics), she could have slipped into a coma and died of respiratory failure, heart attack or acute alcohol poisoning, etc.
Terribly sad to think. But this is why I wonder if KR and her car will be found together on ground and her death ruled an accidental overdose.
The Ram sticker on the rear window is key to finding KR's car if it is not under water. It provides a unique identifier for a common car.
LE should beat that drum loudly (that is, if they haven't found KR's car under water already and waiting on AWS).
ETA: IMO!