That's ridiculous. He left his dog there when the store was closed - no one was "taking care" of his dog but himself. All he was doing was using a cage - nothing more. No one was feeding the dog, walking the dog, playing with the dog, nothing. Firing him for theft of services...
I could understand if he brought his dog there during the day and the employees were actually caring for his dog and he didn't pay for services... but that is insane.