According to the authorities, her son had spent the entire time in the apartment of the suspect, whom they identified only as a 44-year-old German man. He was detained on Friday and was being held on suspicion of a severe sexual crime.
The case resembled two kidnappings in Austria more than a decade ago. One was that of Natascha Kampusch, an Austrian girl held in a windowless cellar for eight years before she escaped at age 18 in 2006. In the other case, two years later, it was discovered that Josef Fritzl had held his own daughter captive in his basement, where he raped her repeatedly, fathering seven children. She and her children escaped, and he was sentenced to life in prison in 2009.
Prosecutors in Bochum said Monday that the man in the German case, identified by the German news media as Lars H., was convicted of possessing child pornography last year and handed a 10-month suspended sentence.
The police said there was no indication the teenager had been bound or suffered any visible abuse. But Ms. Bock said she hardly recognized her son, who told her that he had not been outside since the day he disappeared.
“I was shocked,” she said. “He seemed to me like a broken old man.”
He is now in the care of psychologists, who were assessing his condition. It was not clear when he would be allowed to return home. Before his disappearance, he had been in the halfway house because of behavioral issues related to the death of his father.