I heard it can be found at Granite Cafe in Dewford, well, although you need to have a Mach Bike.
After you enter the first stair down, you need to walk straight. There, you can see a somewhat muddy ledges, different from the others. Wear you Mach Bike, and ride it, crossing the muddy ledges. Then, you have some chances to get Nosepass, as a wild pokemon of course.
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you catch nosepass at mt. coronet
Nosepass is a swarm Pokemon on Pokemon diamond
you catch it in granite cave
On the Pokemon Emerald, Ruby, and Sapphire games; there is no evolution for Nosepass. It comes in the Pearl, Diamond, and Platinum games. Hope this helps.
Wild Nosepass can occasionally be found in the Granite Cave by smashing rocks (via HM06) in both Ruby and Sapphire. Too bad you can't just swipe Roxanne's; that'd be a lot more fun.