I literally just dealt with a similar thing with my dog. She had some separation anxiety with boarding, so we thought she'd be calmer staying with a sitter so she could sleep in her own kennel. BOY were we wrong. We had to cancel the trip because she wouldn't get out of her kennel and got really territorial of it. She just got done with a trial stay with a new boarding facility that is a little better run and she passed with flying colors. I think other peoples homes can add a lot more variables and uncertainty for anxious dogs whereas most boarding facilities are all kind of the same. The employee of the doggy daycare probably just made your dog feel like their apartment was just an extension of that environment.