To me i see nothing to suggest that LE hasn't done a thorough job.
Also, there is zero evidence that she was merely considered a runaway. LE has never stated that. Only the dad and SM have.
The FBI and NCMEC got involved two weeks after she went missing.
Karlie Gusé Update: FBI, NCMEC joins search for missing girl who may have walked away ‘disoriented’
"Despite an extensive air and ground search, an investigation by local law enforcement and the FBI, and nationwide publicity, no clues have surfaced in the mysterious case.
Last weekend the sheriff’s office in Mono County, California, which is leading the investigation, searched the desert with cadaver-sniffing dogs.
But when Zac phoned Lindsay, she urged him to call the police, so he dialed 911. That afternoon the Mono County sheriff’s office launched a search and rescue operation.
According to Sgt. Clark, the weeklong effort involved multiple helicopters, half-a-dozen scent dogs and upward of 60 personnel.
Rex Hamilton, a neighbor who watched the search unfold, told the Review-Journal, “This is a quiet little community, but for a few days it was like ground zero up here.”
The sheriff’s office also enlisted help from the FBI in analyzing cellphone data and pursing leads."
Search continues for California teen Karlie Gusé