A restaurant is, by definition, a public place. Being in a booth doesn't give you carte blanche.
Seriously, this is pretty standard in the professional world. I'm a teacher. We had a whole-day seminar during my degree about the importance of managing your public appearance on things like Facebook. They had concrete examples. Like one girl, who was fired from her teaching position, and her teaching license revoked, because of one pic on her public facebook that had her with a red solo cup and a pirate hat on, with the tag "drunken pirate". That's it. She appealed this in court, and lost.
If you've posted it to the Internet, it's public. If you say anything somewhere it could be overheard, it's public.