That reminds me of a time my girlfriend and I were in San Diego for Comic-Con and the same thing happened to us. We went to a fairly fancy and very eclectic restaurant called Kelvin in a hotel in downtown San Diego.
We were seated around 6:30 PM and there wasn't another soul in the place. It was small, but probably still had a capacity of 60 or so diners. We ordered drinks, then appetizers, and eventually our meal. 35 minutes after we had sat down, there were still no other customers. I joked to my girlfriend that I had reserved the entire restaurant just for us.
I got a little worried about the quality of the food, but it was fantastic. I had a filet, and it was easily in the top 10 steaks I have ever eaten. I think she had duck, and it was also incredible. At about the 45 minute mark, one guy came in, sat at the bar for about 10 minutes got a take-out meal and left. Then, when we were having dessert, probably around 8:00 a group of 5 or 6 people came in and stayed for dinner.
It was just the weirdest thing - to be attached to a hotel, that was probably sold out due to Comic-Con, and not have a single other person in the restaurant. It's possible they did really well later at night, I guess. That was about 5 years ago, and since then the hotel was sold and Kelvin no longer exists.