I really think LE gave big clues in the press conference as to what they think happened, and I’m in that camp too. But since they haven’t named a POI yet can’t discuss it here.
In the meantime, here’s the scenario that crossed my mind before the press conference. What if K went for a day flight w/another pilot that needed hours to keep current? It’s been a while since I flew and rules may have chamged but private pilots used to have to do three take-offs and landings every three months to keep their license current. Often that involved a few hours in a plane doing touch and go’s or flying to a nearby airport, landing then taking off to another nearby airport, landing, maybe seeing some local sights then returning home. It can get boring and isn’t unusual for a pilot to invite another pilot w/them for company.
I can imagine someone K met at a nearby airport saying “you aren’t doing anything for Thanksgiving? I’m not either. Do you want to keep me company while I get my hours?”
If they picked her up at home K would likely have taken her purse but nothing else. That person could have flown pretty much anywhere, taken her “out for lunch”, assaulted her once away from the airport and abandoned her body. He could return the rented plane as expected and no-one would know she’d ever been with him.
Conceivably he could have rented the plane for several days and flown to Idaho w/her phone. They only charge you for engine hours and over Thanksgiving weekend no-one would bat an eye at a plane being used for 4 days. Yes, he’d have to refuel but random private planes land all the time at airports to refuel — no-one would give it a second thought. If he was flying VFR there would be no need to file a flight plan and unless someone knew to try and piece together where that plane went, no reason anyone would ever suspect him.
If LE doesn’t have any solid leads, they might want to look at private planes that landed near the area where the cell phone pinged that day to see if any were from Colorado.
But, I suspect LE has other more promising avenues to explore.