Yes, unless we think it was a Virgin Birth then some dude must have been the father. But that doesn't mean anything else about her story is true. And even if she is telling the truth about his name being Andrew Norris

, there's no guarantee that he gave her the right name to begin with.
I'm not convinced that the police did such a terrible job of looking for him either. I'm usually sceptical of police
but the only real problem the journalists have found so far is not checking phone records for the months just after Tegan's birth. Rental and sublet records are always patchy, and it's the job of the defence lawyer to look for any flaws in the investigation no matter how tiny or irrelevant.