If it was like anything I'd experienced, the "empty" seats were probably reserved for someone else, so after a time or two of being told that, OP and her DH went to an empty table.
Another story: When I first started at Evil Oil Company (and everyone groans), They had an annual holiday party at the country club. The receptionist, "Randi," had previously asked if I would sit with her, so when we got to the venue, I was hanging out with Randi as she, for some reason, was counting chairs at a particular table. Until I realized, that during her "Bill will sit here, Beth will sit there," she had assigned every seat at her table without mentioning me. I said something to that effect and Randi responded, "Well, you're not sitting with us." This total turnaround was so humiliating to me that I simply got back in my car and returned to work. My lead saw me return, and knowing that I had left with Randi (heck, she rode with me), figured out what happened and went to the supervisor. They both tried to convince me to go to the party with them, but that I felt that would have been even worse, so I remained at work (thankfully by myself) for the rest of the day.
Randi was later raked over the coals by supervisor and lead, and she confronted me for getting her into trouble, so I told her that I hadn't said a word, that lead had figured it out on her own. Randi never forgave me for somehow letting it be known that she had mistreated me.