The man was one of 200 people who telephoned police after Claire's partly-clothed body was found in woods near her home in Cardiff on Thursday. It is thought she was a victim of a sex attack.
The man called police 24 hours after Claire's body was discovered. Detective Superintendent Colin Jones, who is leading the murder inquiry, said: "We urge him to contact us again, and he can be sure we will speak to him in complete confidence."
Claire disappeared after she left home on the St Mellons estate at lunchtime on Wednesday, apparently intending to walk to Rumney High School. Her body was found the next day by a cyclist 25 yards from a woodland path.
But detectives now believe that Claire, who had a history of truancy, may not have been telling the truth when she told her mother, Pam Bennett, that she was going to school.
A 16-year-old boy has told police he saw Claire walking near shops on the estate.
Mrs Bennett issued an emotional appeal for anyone harbouring the killer to contact the police.
"If anyone is guarding him, they should stop and think what he has done to my beautiful daughter," she said.
"Any mother who suspects her son, any wife who suspects her husband, or any girl who suspects her boyfriend should ring the police immediately.
"I appeal to them, woman to woman, not to protect this evil man," Mrs Bennett said.