Did everyone know the dog would be going to the meal?
It sound like the others, once they got to the pub just headed off into the restaurant without thinking about your dog. I'm assuming there wasn't any proper discussion about where to sit?
Maybe they hadn't even realised the dog wasn't welcome in the restaurant area?
What often happens in a group is that one person heads off and others follow.
It may well be that there was no intention to exclude you. 
Daughter in law from hell, mini videos on Facebook…
What has survived in your garden with minimal or no watering?




