A 15-year-old Michigan girl has gone missing in what authorities described as “suspicious” circumstances after she did not return home from school and her cellphone was found abandoned.

Adriana Davidson, of Ann Arbor, last contacted her family about 9 a.m. Friday while on her way to Pioneer High School, where she was last seen by friends two hours later, ClickOnDetroit reported.

John Davidson she he last heard from his daughter — whom they call “Addy” — when she left to take a public bus, but she never returned and failed to respond to his texts.

“We’re going on what, Day 2 now? This is not my daughter,” Davidson told 7 Action News.

After checking with her friends and going to the school to look for her, the frantic dad contacted the Washtenaw County Sheriff’s Department.

Department spokesperson Derrick Jackson told the news outlet: “There’s definitely some suspicious pieces to this.”

Investigators checked surveillance video from the bus and discovered that Adriana arrived at school Friday morning but left soon after. Friends told police she felt unwell.

Other video showed that the girl returned to school about noon but never went inside, according to the news outlet.

“We have no idea at this point, so that’s why we’re asking for the public’s help,” Jackson said when asked if investigators had any idea where she went.

Adriana’s brother Anthony Lopez said one of the girl’s best friends told him she texted her.

“The text messages between her and her friend are time-stamped at 12:26 p.m. where she had texted my sister saying, ‘You straight?’ and then Addy responded saying, ‘No,’” Lopez told 7 Action News.

When the friend reportedly texted “Wym,” an abbreviation for “What do you mean,” Addy never replied.

On Friday afternoon, a student found Addy’s cellphone on the school’s tennis court and gave it to Addy’s best friend, according to the outlet, which said police have the phone.

“When I found out that Addy was potentially missing, I knew right away she didn’t run away. The red flag for me was the phone,” Lopez said.

“I know that wherever she’s at, she’s not there willingly,” he said.

Jackson told told 7 Action News: “What teenage girl just wanders off and leaves her phone and doesn’t contact someone?”

On Sunday, the family handed out fliers of the missing girl throughout Ann Arbor.

Anyone with information is asked to call the Washtenaw Sheriff’s Anonymous Tip Line at 734-973-7711, or the Washtenaw Sheriff’s Dispatch at 734-994-2911.