I live in a town where everyone knows each other. If a friend knew I had an appt that morning and hadn't been able to get in touch with me, I could see this:
Friend calling doc: Hey, I've been trying to reach Mtnlites all morning. She's not answering and I'm worried about her. She wasn't feelung well last night. I know she has an appt there this morning. Can you just tell her to check her messages?
Doc office: Gee sorry, but she didn't come in this morning.
A violation if HIPPA, sure, but it happens. I am FB friends with the whole staff at my PCP's office. Lines get blurred. Ultimately, though, I feel like this is a total nonissue.