If you live in a house or something with a backyard have you considered a doggy door so he can let himself out?
Duke has run of the house when we leave, and when I have day classes and he is left, he tends to pitch fits and pee on the floor even when a potty pad is out, he pees somewhere else..it's his way of getting back at me I guess
Doggy doors can be expensive, but if they learn how to use it, it can be a life saver.