Where did you find it in White 2?
Sawk - game locations
Outside Pinwheel Forest, Routes 15, 18, 23 (tall grass B2/rustling grass W2)
Victory Road (rustling grass)
^ Those are the locations for Sawk in White 2. If you found it anywhere else, it was a glitch.
I'm also not sure where you got the 0% figure from. I think you might have confused it with its gender ratio; Sawk is a male only Pokemon, therefore its male ratio is 100% and female ratio is 0%.