Ask the boarding staff what they actually observed: times outside, urine and stool passed, appetite, water and any signs of straining. Do not assume that access to an outdoor area proves your dog used it. A long pee after pickup does not prove when they last urinated, and it does not tell you what happened during the stay.
If your dog repeatedly tries to urinate but cannot, seek emergency veterinary care. Pain, a swollen belly, vomiting, marked lethargy or not passing stool as usual also needs prompt veterinary advice. The article on preparing a first boarding stay may help you plan future questions about the routine, but it does not replace checking your dog now.
Once a vet has addressed any medical concern, ask the facility about the dog's usual toilet spot, whether they were watched in an unfamiliar run and whether the schedule matched home. Some dogs need a quiet lead walk or more privacy to toilet. Arrange a specific care plan for a future stay rather than assuming they will eventually adapt. Do not punish any accident after pickup.
Today, record the dog's last known urine and stool, current drinking and behavior, and call the vet if the pattern is abnormal. A clear record matters more than guessing why the kennel felt different.
Sources: VCA on urinary emergencies, VCA on constipation signs, Dogs Trust on stress and changed behavior.