Robert, hang in there! It can be confusing if you get ribs where the membrane has already been removed. I buy ribs at Costco and the membranes have been removed at the packing plant before they ever hit the door at Costco. I wonder if it's the same at BJ's?
Len's photo-s is a great look at what the membrane looks like if it's there. It's very smooth and shiny, and if it's been removed what's under it is not so smooth and shiny. But even I get fooled sometimes when I go to skin a rib and realize it's already been done, so don't feel bad if that happens to you!
Good luck,
Chris