Obviously, we aren't privy to the information we want to have about the time discrepancy, which is fitting. I'm willing to bet that police have all the information they need about the situation with J and J's dad that morning. What they don't know is what happened to Jessica between her front door and the park.
Or if the kidnapping even happened between her front door and the park. I'm still not clear if she was headed to the park or to the friends house?