If I find hair in my food I just pick it out and keep eating. It would take too long to send it back and get more and when I'm hungry, I'm hungry! Besides, I'd be more worried about somebody spitting in it when I sent it back.
The food would have to be superb in order for me to forget about an uncovered beard. The way I look at it is certain jobs require certain appearance and dress code rules; a chef should be clean shaven IMO or at least have a covered beard at a bare minimum.