It's not there for me though ive been where you told me to go
I suspect you didn´t go far enough into the cave. Follow the description I gave you. If you did it right, you´ll have gone:
Up a slope, down a ladder, up a slope, up another slope (on your right hand), down a slope, and finally down a second ladder located at the bottom right hand side of the "main" room. On this floor, which would be two floors beneath the Cave Entrance, you really should be able to find Sableye / Mawile.
Coincidentally, this is the same room where you find the Everstone.
Anyway, I´ve got to make some dinner and stuff. There is no doubt that Mawile is in Granite Cave on the bottom floor along with the Everstone. I´ve been unreasonably patient, waiting half of Saturday for something that took me 5 minutes to do (albeit, I only have Sableye). I´ll be back in a few hours - hope you´ve figured it out by then.