Like a lot of teenage girls, 15-year-old Sierra LaMar used her smartphone as her billboard, her diary and her mirror. She sent text messages, tweeted and composed self-portraits of a petite, dark-haired beauty who liked makeup, cheerleading and dishing about reality TV star Kim Kardashian.
That electronic window into her world now sits in a San Jose crime lab undergoing forensic tests.
Sheriff's deputies found the device March 17, the day after Sierra's mother reported her missing. It was in a field near where she normally caught a school bus in Morgan Hill, a semi-rural community of 40,240 on the fringes of Silicon Valley surrounded by mountains, orchards and reservoirs.
On the day she disappeared, Sierra, a sophomore, never made it to the bus or her high school.
After initially allowing for the possibility that Sierra ran away from the home she shared with her mother and her mother's boyfriend, the 40 detectives assigned to the case are saying they now believe it is highly unlikely that she vanished voluntarily.
Their conclusion was based on Sierra not having a history as a runaway or any unusually negative family problems. Interviews with friends and a search of her computer also yielded no information indicating she fled.
For her family and many of the 583 volunteers who turned out to search for her, Sierra's abandoned phone wiped away thoughts that she ran away.
"A teenage girl without her phone? No way," said Gwen Dorcich, a mother of two teenagers who showed up at a vacant elementary school that was transformed into the search command center to sign up as a volunteer. "If she was planning to run away, she was going to tell friends that."
So far, however, the investigation has provided more questions than clues.
The day after deputies located her Samsung Galaxy smartphone, they came across Sierra's handbag a few blocks away. Several items of her clothing _ a San Jose Sharks T-shirt, pants and undergarments _ were folded neatly inside.
Tracking dogs lost her scent at the end of the driveway of her home on a cul-de-sac, leading investigators to hypothesize she never got much further.
"This seems like a very remote location, and it seems like anybody who would have been there had to have a reason to be there," said Marc Klaas, whose 12-year-old daughter Polly was kidnapped from her Northern California home in 1993 and murdered.
"Therefore, my immediate thought was: Whatever happened to Sierra, assuming she did not run away, happened on this block," he said.
A missing children's foundation he founded in his daughter's memory is organizing searches in the city, about 25 miles south of San Jose. Of the 46 similar searches the KlaasKids Foundation for Children organized last year, 37 resulted in either a victim being found alive or their remains located, he said.
The law enforcement response has included searching the homes of neighbors, contacting registered sex offenders, interviewing friends and relatives, and stopping drivers who travel the road where Sierra picked up the bus and where her phone and purse were found to ask if they saw anything unusual.
On Tuesday, a sheriff's team boarded a boat with a cadaver dog to search the shores of Calero Lake, a reservoir and teen hangout, while volunteers walked the surrounding brush-covered slopes in a line formation.
A weekend search by the sheriff's department and the FBI covered a 12-square-mile radius from Sierra's home. It included canyons and hillsides off major highways that could provide a place to dump something in a hurry, Sheriff's Sgt. Jose Cardoza said.
People have called in tips about seeing a girl matching Sierra's description, he said, but none had panned out.
"We do not know what she was wearing when she left the house, we don't know when she left the house because no one saw her do it, and we have not had any new credible leads or tips or evidence since discovering the bag of clothes," Cardoza said. "There has been ... so many unknowns."
Sierra's mother, Marlene LaMar, told investigators she last saw her daughter when she left for work about 6 a.m. on March 16.
Just before 6:30 a.m., when Sierra ordinarily got ready for school, the teenager tweeted. A friend received a routine text message from her about 40 minutes later, the time she usually left home to catch the bus, authorities said.
But investigators have not found anything to signal where to look now.
The MacBook she got for her birthday has not provided any hints about where she might be. The night before she disappeared, she tweeted that she planned to write a school essay about teen depression and suicide. That same week, she tweeted: "suiiiiicide im tooo aliiiiive kill ya sellf."
Sierra and her mother have been living in Morgan Hill since October. Tonya Miller, a family friend, said Sierra appeared to have adjusted to the move, briefly joining a private cheerleading club and befriending the daughter of her mother's boyfriend.
The sheriff's department said neither Marlene LaMar nor her boyfriend is considered a suspect.
Authorities also absolved Sierra's father, Steve LaMar, a registered sex offender convicted in 2009 of one count of lewd or lascivious conduct with a child under 14. The victim was not Sierra or her older sister. Police say he is cooperating in the investigation and is not a suspect.
"I'm not going to hide it. It is very important they interview me, I get cleared and cooperate with everything," LaMar said.
The night before Sierra went missing, she asked her father to make an appointment to get her hair highlighted. He said he texted her the next day to say he had, but never got a reply.
When investigators reported finding the phone, Steve LaMar said, "That was pretty disturbing because we know that she is 15 years old and she loved that phone and was always on it. We would get mad at her for being on it at dinner."
Among the hundreds of volunteers Tuesday were several who endured the same ordeal as Sierra's family.
One was retired San Jose Police Officer Pat Boyd. His 28-year-old daughter, Cristie Wilson, disappeared from a Sacramento-area casino in 2005. A man who gambled at the casino that night has been convicted in her murder, but her body never was found.
On Tuesday, Boyd stood in the command center, explaining to volunteers returning from a fruitless search that their effort was still valuable not just to investigators trying to narrow the territory they have to cover but also Sierra's parents, who have only question marks.
"Do I hope and pray she is just a misguided teenager and ran away? Yes, that is my number one hope," he said. "Number two is that somebody did abduct her and is keeping her alive somewhere. And the last is that at least the family gets closure by finding out who did it and where she is."