Time for Steve Coolbaugh these days is measured in “since she left.”

“Today is day 22 since she left,” the Cotati resident said Monday. That is, it has been more than three weeks since his wife, Mimi, has been missing.

Noemi “Mimi” Coolbaugh walked away from her sister’s home in Gilroy last month under unexplained circumstances. She hasn’t been seen or heard from since.

Gilroy police haven’t been able to devote many resources to her case, not having any suspicions of foul play.

Cotati police have checked on her residence there and have helped Steve Coolbaugh begin his own searches, but acknowledge that there’s not too much to be done with no clues to go on.

The situation is complicated because Mimi Coolbaugh is an adult and apparently left of her own volition, although she likely is depressed and may have had suicidal thoughts, her husband said.

“I was going through my mind this morning trying to get in my wife’s head,” Steve Coolbaugh said. “For her to have left that morning, she had to have been in so much pain.”

Their teenage son has been treated for mental health issues, he said, and Mimi was depressed that he hadn’t been doing well recently.

The couple has run a computer networking company in Cotati for the past 14 years.

Mimi Coolbaugh, 49, was last seen around 7:30 a.m. June 22 when she left her sister’s house on foot. She didn’t take her cellphone, keys or purse, Sgt. Pedro Espinoza said.

She is described as 5 feet, 5 inches tall, about 130 pounds with brown hair and brown eyes. She wears eyeglasses.

Family members, friends and Gilroy police searched Coolbaugh’s sister’s neighborhood in the first days after she went missing, with no results.

Steve Coolbaugh has received help from the missing-person help agency KlaasKids and friends of Sierra LaMar, a teen girl who authorities suspect was abducted in Morgan Hill in 2012 and who is believed dead. The group’s volunteers search every week for her and offered assistance to Coolbaugh.

Coolbaugh has mixed emotions about the unsuccessful searches, which include helicopter searches of the Gilroy area.

“We hired a private investigator and they went down the railroad tracks from San Jose to Gilroy with drones. They didn’t find her there, so that’s good to know,” he said. The LaMar searchers combed hiking trails last weekend. “They concluded she’s not there,” he said.

While it’s disappointing to not find her, at least there’s hope she’s alive, he said. “As close as she was with her mom and her son, for her to have walked away … the only way she could have done that is if she abandoned herself. Knowing the pain she would cause her mother, I’m fully confident her mindset was one of never looking back.”

He thinks she may have taken a train to the last stop in San Francisco and disappeared into homelessness. None of the couple’s bank accounts or credit cards have been used and Coolbaugh said he went back a month and didn’t find any evidence that she’d planned an escape.

As time passes, he’s expanded his search to Santa Rosa and Petaluma.

Steve Coolbaugh rented the electronic billboard in Rohnert Park along Highway 101 and spent Monday evening in Santa Rosa passing out fliers with his wife’s image and contact information.

“I think the mindset was to get away,” he said. “But she could be out there. I’m just asking and begging anyone to help get the word out.”

Coolbaugh is buoyed by stories that end well. A Petaluma man who went missing showed up safe recently after being gone for three weeks.

“I hope people will keep their eyes open, just in case,” he said.

Anyone with information is asked to contact Gilroy police at (408) 846-0350.

You can reach Lori A. Carter at 762-7297 or lori.carter@pressdemocrat.com. On Twitter @loriacarter.