Search and rescue effort continues for longtime auto journalist Davey Johnson

Johnson was on assignment for Motorcyclist magazine.

Authorities are actively searching the foothills of the Sierra Nevada mountain range for Davey Johnson, a veteran auto journalist who disappeared five days ago in the tiny town of Mokelumne Hill, California.

Johnson, who was testing a Honda CB1000R motorcycle as part of an assignment for Motorcyclist magazine, had briefly detoured into town after driving through the mountain range on his way to Sacramento, where he lives, according to his fiance Jaclyn Trop. She alerted the Calaveras County Sheriff's Office on June 7 that he was missing.

"I never go more than 12 hours without talking to him," she told ABC News by phone. "We were supposed to meet up in Salt Lake City on June 8."

The last contact she had with Johnson, 43, was at 5 a.m. ET on June 5 when he sent her a text message, assuring her he was safe.

"I left the summit about dark, which had me worried about ice so I was going on no miles an hour for a while, and then I was just so tired that I stopped to rest a few times," he said in the text, which Trop shared with ABC News. "But I had a great time before it got dark. That part of the Sierra is just stupidly spectacular. Anyway, I'm so sorry I worried you. Yes, I'm okay and alive, but I am WIPED. I love you very much, Jaclyn Sara Trop!"

According to Trop, the motorcycle Johnson was driving was located by authorities near the Mokelumne River, where Johnson allegedly went for a swim. His backpack, clothes, cellphone and computer were found by authorities. His wallet was recovered a few days later.

Trop said she fears Johnson may have drowned in the river.

"He was probably swept away in the river," she said. "The detective said the current has never been so fast and so high. He's not really an experienced swimmer."

A search and rescue team spent Saturday and Sunday combing through the Calaveras County region off Highway 49 looking for clues. Helicopters, dogs, drones, boats and foot patrols have all been deployed, according to police.

Lt. Anthony Eberhardt of the Calaveras County Sheriff's Office told ABC News Tuesday that the search for Johnson is "ongoing and very active."

"We're trying our best for a successful recovery," he said. "We're utilizing any type of means."

Eberhardt said California Highway Patrol and police departments from Amador and Tuolumne Counties have contributed resources to the rescue effort. Police do not suspect foul play, he added.

Johnson, who was one of the first employees at Jalopnik, an auto review website, gained fame for his reviews at Car and Driver magazine. Jonny Lieberman, senior features editor at Motor Trend, first met Johnson in 2002 in Los Angeles and the two later worked together at Jalopnik. Johnson is "loved by everybody," Lieberman told ABC News, adding that Johnson has been incredibly influential in the cutthroat auto journalism industry.

"He told me he had never been happier and he had the perfect girlfriend," Lieberman told ABC News. "Everything was going his way."

Chris Cantle, editor-in-chief of Motorcyclist, said Johnson has a way of turning "mundane things into an adventure."

"Johnson could have taken the freeway to Sacramento from Irvine," he told ABC News. "He was riding alone in the mountains but has good judgment. We trust Davey."

Julia LePalme, Johnson's friend and industry colleague, said Johnson always makes an effort to keep in contact when he's alone on a drive.

"He is an avid motorcyclist," she told ABC News. "He was probably exhausted and fatigued and suffering from elevation sickness."

She added, "He's a road warrior. He loves these road trips."

Trop said she and Johnson were going to officially announce their engagement next week. They were both looking forward to an upcoming trip on the Queen Mary 2 cruise ship.

"He's just incredible. Like magic," Trop said. "There's no one like him."