Thanks to all for your encouragement. Perhaps with the leaves gone he will have less camoflage.
I still keep an eye out for him whenever I am out and about and continue my vigil of checking HS websites although our Oakville HS has been closed due to a cat virus for a couple of weeks now making it impossible to check ("cat room is temporarily closed").
Like Jayne, I don't believe I won't see my big boy again. I have enrolled at Pet Lynx as they are connected to other out lying HS and have a cool registry which searches shelters based on markings of the animal. I wish all the shelters would sign up for this as it is really good.