Updated

No one claims to know what happened that summer in 1999 when 11-year-old Adam Herrman disappeared from the mobile home park where he lived with his adoptive parents.

But the biggest mystery may be why no one reported him missing until nearly a decade later.

The search for Adam — who would be 21 if he is still alive — has confounded authorities and left family members regretting that they did not do more when they noticed he was gone.

His disappearance finally came to light last week when authorities — acting on a tip to the Sedgwick County Exploited and Missing Children's Unit — searched the empty lot in Towanda where the family's mobile home once stood.

Butler County Sheriff Craig Murphy has refused to say much about the case except that no human remains were found during the search.

The publicity around the search has spawned a flood of tips to the sheriff's office. More tips are expected following Tuesday's release by the National Center for Missing and Exploited Children of a computer-enhanced photo showing what Adam might look like today.

No charges have been brought against his adoptive parents, Valerie and Doug Herrman. Murphy said consideration of any charges would wait so officials can concentrate on the search for Adam. Investigators plan to scour the banks of the Whitewater River just west of the mobile home park on Saturday.

Doug Herrman, who lives in Derby and owns a masonry business, said Tuesday that the family would not comment.

Family attorney Warner Eisenbise said Adam had a history of running away and that the Herrmans feel "very guilty" they did not report him missing. The family assumed he had found one of his siblings or went back to his biological parents, he said.

Asked on NBC's "Today" show Wednesday if his clients had anything to do with Adam's disappearance, Eisenbise replied: "Not at all. Nothing at all."

The boy's biological father, Irvin Groeninger II, also expressed regret. The Indiana trucker was divorced when authorities took Adam and his siblings from their mother's home after alleged abuse. He says he was cleared of any wrongdoing and tried to get custody of his children, but child welfare officials terminated his parental rights.

"Basically, I have lost him twice," Groeninger said.

The boy — whom he knows only by his birth name of Irvin Groeninger III — was 18 months old when Groeninger last saw him. He had hoped his son would try to contact him when he was old enough to search for his biological family.

He says he wishes he could tell his son: "I love him and I wish I had fought harder back then to get him and keep him in my custody."

While Adam and two younger siblings were adopted by the Herrmans, Adam's older biological sister, Tiffany Broadfoot, was adopted by another Wichita family. Broadfoot has not seen her brother since a birthday party when he was 7 or 8 years old.

Broadfoot said the first time she called Adam's adoptive mother she was told everything was fine and Adam was doing well. Other times she was told not to call again because Adam and his siblings did not know they were adopted.

In August or September, she called Valerie Herrman again. "The last time I talked to her she was very in my face and very adamant: 'You have no business calling here. You have no right. That is not your family. Don't call here. Don't talk to us. Don't do anything. That is not your concern. Back off,"' Broadfoot said.

Linda Bush, a former sister-in-law of Valerie Herrman, remembered Adam as a timid little boy. She has not seen him since he was at least 6 years old.

"He wasn't boisterous, running around making a lot of noise like other children. And he stared a lot. That was strange," Bush said. "He gave me the creeps sometimes because he would stare. But it was nothing to hate him for."

Bush said she remembered Valerie Herrman telling the boy he was stupid.

"It was the tone. It was constant. She constantly berated him and put him down, a hateful tone," Bush said. "It was constant and we couldn't figure out what that boy had ever done to make her hate him like that."

The Herrmans did not treat Adam's two younger siblings the same way, she said.

Bush said she first heard Adam was missing last month, when Valerie Herrman called her and said police thought the boy was missing and may have been murdered. That was the first she heard that Adam had a history of running away.

Bush said the Herrmans told other family members that they had turned Adam back to the Department of Social and Rehabilitative Services. She said she had no reason to believe otherwise because the couple had other foster children who went back to state custody.

"They had turned other children back, whether voluntary or mandated," Bush said. "Nobody had any reason to disbelieve. Who would think of something so heinous happening? Nobody did."