Im not sure!...Its possible that your dog was keying in on that...they rely on smell about as much as we rely on sight....imagine having to live with a person that wore neon colors.... :::shutters::: If the groomers reminds him of happy stuff It could definetly make the new dog remind him of happy stuff! I know I smell som'thing randomly and have happy childhood flashbacks...im sure dogs make those associations too.
Emma gets really wierd like that too when a temporary dog is around...I think the change in routine confuses (or frustrates) som' dogs... In fact Emma gets so "wierd" that we pretty much make it a point to keep the temporary dogs outside now. She seems confused by them.
Can't wait to hear about the new little foster girl if you get her.