We already know that there has been people before us, and their physical appearances can be changed by the town. Billy Smith and the Librarian are the best example: he didn't sound at all like a young boy in that phonecall, did he? So it's possible that the girl who originally wrote this has been changed to someone else too. But even then, it's possible that she's no longer in Mayfield. The odds are very slim; would you have any idea where to start? [...She wanted to say impossible, really, but... Ah, there's no use in making that sort of statement, especially when Crowe must be already aware.]