In the fall of 1982, 14-year-old Daniel Naylor walked out of his parents' Fremont, Calif., home after a heated argument with his father and was never seen again -- leaving family and police to believe he had run away.

But a new look at the case some 33 years later has detectives eyeing his disappearance as "suspicious," and digging up the backyard of his childhood home, police sources told FoxNews.com.

"We believe he ran away and had a lot of help doing it or he met with foul play." — Geneva Bosques, Fremont Police spokeswoman

Naylor was a freshman at American High School when he left the home on Nightingale Place at 7:30 p.m. on Oct. 5, 1982, according to his father -- who police say was the only family member home at the time.

A search by neighbors for the boy -- who was reported missing some 10 to 12 hours later -- uncovered his bike near brush along the Alameda Creek Trail, a short distance from his home.

A bizarre clue would come one month later.

According to police, the family reported that Naylor returned to their home in November -- when no one was home -- and took $50 in cash and all of his personal belongings.

In his bedroom, the family said they found a message fashioned from Scrabble tiles, spelling out the words, "new life," according to Fremont Police.

"The assumption is that Daniel returned home," said Police spokeswoman Geneva Bosques. "But there is no evidence of that and there is no witness."

"There were no cell phones or Internet in 1982," she said. "We believe he ran away and had a lot of help doing it or he met with foul play."

It wasn't unusual for Naylor -- who was 5-foot-9 with braces and light brown hair -- to argue with family. Police reports from the time of the disappearance said Naylor would often leave the family single-story home and run down the street to his best friend's house after a family feud.

"He'd hang out there until things calmed down and then head back home," Bosques said. "But this night was unusual because he didn't do that."

Police say they believe the reported argument Naylor and his father had on Oct. 5 turned physical, but they declined to elaborate further. Naylor was last seen wearing a gray half t-shirt, red shorts and high top tennis shoes, according to family.

Inconsistencies in statements made over the years led police to obtain a search warrant of Naylor's childhood backyard over the summer. His parents and sister no longer live there, but the home belongs to a relative.

"One of the cadaver dogs indicated on a scent in the yard," Bosques said. "Based on that search, we were able to obtain a second search warrant for a dig on a portion of the backyard."

"We are not discussing what we did or did not find," she said. "It’s still a very active investigation."

Weeks before the search of the yard, a neighboring police department identified a transient in the area who strongly resembled an age-progressed photo of Naylor, who would now be 47 years old. DNA evidence later concluded the man was not Naylor.

The Naylor family was not available for comment when contacted by FoxNews.com. Naylor's parents and sister, Lori, have not talked with the media in recent years, according to police.

No suspects have ever been named and no theories have been ruled out, Bosques said.

"We’re hoping in a perfect case scenario that he comes forward to tell us that he is, in fact, a runaway," she said. "If he is alive and he's out there and sees this, we’d love to just hear from him and know that he’s OK.

"It would put it all to rest," said Bosques. "Whatever the scenario, we believe that somebody out there saw or heard or knows something. A 14-year-old in 1982 doesn't go into hiding for this long without help."

"Even the tiniest bit of information could really break open this case," she said.

For residents of the small Bay Area community, Naylor's disappearance remains as much a mystery today as it did 33 years ago.

“Some people think he was killed and some people think that he just ran away,” Charlene Forney, a former neighbor who had searched for Naylor, told a local news station.

Anyone with information on the disappearance of Daniel Naylor is urged to call the Fremont Police Department at 510-790-6900 or email ColdCaseDetective@fremont.gov. For anonymoys tips, the public can call 510-494-4856 or text Tip FremontPD followed by a message to 888-777.

Cristina Corbin is a New York-based reporter for FoxNews.com. Follow her on Twitter @CristinaCorbin.