Chris, I'm really sorry to hear about Booker T., especially since I just lost my cat and we would often post pictures of them and their basses.
I haven't really known what to say, but then this morning I thought of something - didn't you move recently, maybe within the last year? Maybe Booker T. tried to go back to your old house? Someone I know moved within the same city, and her cat walked several miles back to the old house through the city of Oakland - twice! Maybe you could post signs or talk to your old neighbors? It's a long shot, but I really really hope you find him.