What makes you think that? Didn't the neighbour in Rexburg meet her? Also, there were Venmo transactions from her phone so could LE work out a location from those transactions? I'll look for the article about the neighbour.
ETA here it is
Mom of missing Rexburg children fled before FBI raid, neighbor says - Local News 8
"Just a week after they moved in, JJ told Seth's son that he and his sister would be leaving soon.
"They told my son that, 'Oh yeah, we're going to go visit my grandmother.' We didn't know where that was. I said, 'Oh, okay,' and I understood because school was about to start. The semester was about to start and she was going to school, from what I understood," Bernard said.
The grandmother told investigators that visit never happened. Bernard didn't notice anything odd about the family.
"The weird thing is there were no warning signs. No 'Hey, there's something going on here.' There was nothing. They were very nice, very friendly. She baked us brownies one time," Bernard said. "
I am wondering if they visited a grandma for Tylee's birthday and she (Tylee) was "starting school" as the "semester was about to start".
So could she be at a religious school?