Sonoma County sheriff's deputies searched Annadel State Park on Thursday for a signs of a 15-year-old Santa Rosa girl who left home Saturday and hasn't been seen since.

Charlotte Anna Molinari, a sophomore at Sonoma Academy in Santa Rosa, had been feeling depressed before she rode her bike away from the family's apartment near Coddingtown Mall about 9:45 a.m. last Saturday, her father said Thursday.

She told him she wanted to go to Spring Lake and Annadel, John Molinari said. He tried to talk her out of going, but she slipped away a short time later, he said.

"It seems now she was planning this," Molinari said.

He called police that evening and a Santa Rosa officer searched the neighborhood without finding her. But there wasn't much more police activity until Wednesday, when investigators searched her bedroom and got a court order to get into her Facebook account, Molinari said.

Police at first assumed she was a runaway, he said.

"Then they actually listened and connected the dots," he said. Meanwhile, some of Charlotte's friends started looking for her, Molinari said.

Santa Rosa Police issued a public appeal for help finding Charlotte on Thursday.

"We developed information she would have gone to Annadel," said Sgt. Lisa Banayat. "We don't have any indication of foul play. We are concerned about her mental status."

Banayat said she didn't know why the department waited until Thursday to release a missing person report.

A sheriff's helicopter searched Annadel on Thursday and the department later set up a command post at Spring Lake for a ground search.

The search ended about 8 p.m. with no report of a sighting.

Molinari was described as 5-foot-9 and 150 pounds with brown curly hair and brown eyes.

She was wearing a dark blue knee-length coat and a green backpack. She also had a ukulele and a laptop and rode a green mountain bike, Banayat said.

"We are really concerned for Charlotte," said Janet Durgin, who heads Sonoma Academy. "We are just so worried."

The sophomore won a scholarship to the private school based on her interest in science, technology, engineering and math, Durgin said. Molinari was involved in music, theater and sports, she said.

"She's very bright and has so many interests," Durgin said.

Sonoma Academy is distributing "missing" posters and her father created a "Find Charlotte" page Thursday on Facebook to help in the search.

"I set up this page for anyone that has any information regarding Charlotte's whereabouts," her father said on Facebook. "Please spread the word and help us find her and bring her home. Since we have started the search, there have been many people commenting on how special she is and how she is loved in the community."

Anyone with information about the case can call Det. Jeneane Kucker at 543-3595 or the dispatch unit at 528-5222.