Talk to one of the meat guys at Costco. Ask him where the whole prime packers are. They are always on the far right hand side of any Costco I have ever been in.
Yes, I plan to go and ask the guys directly, my wife is an employee at that store and hopefully she may know someone in the meat department.
I looked carefully and they do not have the whole brisket on the fridge for sure, they always have both the flat and also the whole brisket side by side, so it is not there for sure for some reason.