Ian Thorpe believed he was sitting in his friend's car when he was picked up by police, according to his manager .
"The owner of the car basically called the police and the police came," he said. "They realised it was Ian Thorpe. They realised he was disoriented."
Mr Erskine said Thorpe, 31, had been taking antidepressants and medication for his shoulder but denied that he had been drinking alcohol."He hadn't had a drink," he said. "He had zero alcohol in him."
Police said no official complaint has been made and no further police action is anticipated.Thorpe, who lives in Switzerland, has been staying with his parents over Christmas.
Mr Erskine's admission that Thorpe is in rehab comes only days after his management company denied reports that he checked into a rehab facility while fighting depression and alcohol abuse.
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The author, who explored feminist themes, was best known for her Earthsea books.