Cat lovers, please help! Any way to stop mine from constantly caterwauling?

My indoor car, a Siamese, got out one day recently and enjoyed three hours in the sunshine and bermuda grass. No worse for wear, but ever since he spends all his time (except when eating) sitting at the door or in the window sill making sounds that are causing my fillings to fall out. Any suggestions? You could be sparing a very nice little cat from being thrown out of the house permanently. ;-)