I'm assuming her computer was checked out..or any of her online profiles/usernames/computers at her high school, etc.
....seems to me like she met someone online and met up with them, especially since she has been spotted many times... Good thing is, she's alive...bad thing is, she dosen't seem to to want to be found for some reason :\
someone posted on her website in her guestbook:
Sarah is in the Beaverton, OR area or so I've heard that from numerous students at GHS. A few even said they've heard from her within the past year and a half or 2 years.
The person didn't leave a name or email...they signed it "GHS student". Perhaps Sarah got in touch with a few select friends and made them promise not to tell where she was? I don't know any other reason why this person wouldn't want to help find her. Maybe an IP search can be run on this guestbook entry?