MOBILE, Ala. (WALA) - For Mobile County Sheriff Paul Burch, it's the one that got away.

Stephen Pearson's disappearance in 2000 was assigned to him as a young investigator with the department.

"That is actually the only unsolved case that I had in my 36-year career," he told FOX10 News recently.

Burch said he believes the missing man was murdered and even has a theory about who did it and why. But no charges ever have been filed.

As Burch recounts the story, a postal worker having trouble finding an address on Wheatcroft Road to deliver a package stopped by Pearson's mobile home on nearby Kingbird Road. Burch said Pearson agreed to sign for the package and deliver it to his neighbor.

Only, Pearson mistakenly put it on the porch of a home on Wheatcroft Road South. It was supposed to go to Wheatcroft Road North. Burch said when Pearson checked to see if his neighbors got the package, he discovered it had contained marijuana. He threatened to go to the authorities if his neighbors did not, and that's exactly what he did, according to the sheriff. That, he said, was the last time investigators believe anyone saw him.

"It's one of those we feel pretty certain, you know, who the parties are who are responsible but, you know, the body's never been recovered," he said. "It's just, you know, one of those cases you never forget about because, you know, we don't have justice for the family or the victim."

Burch said there never was hard evidence to make an arrest. But law enforcement officials eventually brought drug trafficking charges against the neighbors who kept the marijuana.

Pearson's daughter, Julie Pearson, recalled that horrible day she found out her father was missing. She said it was Dec. 27, four days after his birthday.

"The phone rang, and I was in bed, and a minute or so later, it rang again," she said.

Pearson said she was shocked to learn that no one could find her father. She said she also tried but failed to get ahold of him. She said a man who lived down the dirt road from her father told her he saw his car leaving the neighborhood.

"That was it," she said. "That was the last time any of us saw him."

Pearson said she later discovered her father has reported a break-in and added that she saw signs of a break-in. She said a load of clothes still was in the washing machine.

Pearson said her father was a Army veteran who worked at Northrup Gruman in Mississippi as an industrial engineer. She said he was generous, often chopping wood and delivering to neighbors in need on cold nights.

"Daddy was high energy," she said. "His nickname was Rabbit. ... My dad was a good man. He'd literally give you the shirt off his back. I've known him to stop and help a car accident - one accident digging a baby out of a car seat from a seat being scrunched."

Pearson's truck eventually turned up in a wooded area near Henderson Farm Road. But the sheriff sats it was "obviously staged." A massive search involving dogs and dozens of volunteers failed to find him.

Julie Pearson said in her mind, there are at least three groups of suspects - the people who received the marijuana package, the people that package was intended for and the people who mailed it. She says it could be any of them - or perhaps, none of them.

"So no, I'm not convinced foul play is involved," she told FOX10 News. "I'm not convinced that he didn't get out and disappear on his own. He had the resources. He had the knowledge. He had the know-how. I'm not convinced that it's pure foul play. Evidence points in both directions. It's a tie."

A group called Alabama Cold Case Advocacy released an age-progression photo showing what Stephen Pearson might look like today. And the group plans to put up a billboard in the Grand Bay area.

Burch said the department periodically revisits the case. He said he personally took a run at it about six years ago. He said it always helps for cold cases to get fresh eyes. But he added that it likely will not be solved unless someone who was involved - or someone with direct knowledge - comes forward.

"The bottom line is we never give up," he said. "And you know, yes, it's been 25 years. But, you know, any relevant information we will follow up on any and all tips. And we never, ever, ever give up on a cold case."