Authorities in northern California are searching for a Sacramento-based automotive writer who has been missing since taking a motorcycle on a test drive last week through one of the highest passes in the Sierra Nevada mountain range.

Davey G. Johnson, 43, was last heard from when he texted a friend around 8:30 a.m. Wednesday, saying that he was sitting near a creek before heading home, according to Car and Driver.

The motorcycle Johnson had been testing for Motorcyclist magazine — a black Honda CB1000R — was found parked on its kickstand at a rest stop, along with his helmet and gloves, shortly after midnight on Saturday, Car and Driver said. His phone, laptop and backpack were discovered by a nearby river.

Johnson's girlfriend, fellow journalist Jaclyn Trop, last heard from Johnson at 2 a.m. Wednesday, according to Car and Driver.

"I just really hope he's alive, because thinking about the alternative yesterday was ... I don't even have words for it," Trop said. "I was completely gutted, and I would still feel that way if they hadn't found the bike."

Johnson and Trop spent the previous weekend together in Los Angeles, riding around the city on the bike Johnson was testing, before he headed to Las Vegas on his own, according to Car and Driver.

From there, Johnson continued on to Mammoth in California and then to the Sonora Pass, Autoweek reported.

In his last text to Trop, Johnson apologized for being out of touch, according to Car and Driver.

"I had a great time before it got dark," Johnson wrote. "That part of the Sierra is just stupidly spectacular. Anyway, I'm so sorry I worried you. Yes, I am okay and alive, but I am WIPED."

In a June 8 press release, Lt. Anthony Eberhardt of the Calaveras County Sheriff's Office said that the department was notified of Johnson's disappearance on June 7 and searched the area around his parked motorcycle with "negative results."

"Search efforts are continuing," the release said.

Abigail Bassett, a friend of Johnson's, has been updating her Twitter profile with information about the ongoing search. Bassett wrote that search efforts included 45 people searching both sides of the river, as well as searches from two boats and one helicopter.

Although several of Johnson’s belongings were found near the bike, his wallet was missing, according to CBS. Officials have warned that the state's waterways are running cold and fast as snow begins to melt and pour water into rivers and creeks.

"We always talked about having 40 years together, and we had a 40-year timeline and to have that cut short ... is horrible,” Trop told CBS.

A GoFundMe page had been set up to support Calaveras County Search and Rescue's efforts, but the campaign was paused after exceeding its $15,000 goal in 18 hours.

Anyone with information or potential sightings should call the Calaveras County Sheriff's Department at 209-754-6500.

Contributing: The Associated Press