Doubtful they knew the reservation in Sanders was THAT Sanders. It’s a common name and I’m sure it wasn’t made making mention of any connection with Administration.
I just cant get over how fast that a spontaneous protest happened at the other restaurant. Sanders is a common name but if Sara’s name was dropped to the person taking the reservation or the family had made reservations in the past I can see the restaurant finding out ahead of time. I have worked in restaurants as kitchen staff it is surprising what information can be gleamed from a telephone reservation. often time the telephone number of the person Making the reservation is kept and if it is repeat business you know the identity.