Yes some dogs will hold their bladders and bowels so long that they can get an infection. I had a mini dachshund years ago who would not "go potty" no matter how many times he was walked, he would go in "his area" and no where else. Unless your baby is like this, I think I would be doing some checking of the establishment and some major complaining!
Also, is the vet connected in some way to the boarding facility? Why skirt the issue...?