Some of the best experiences with long hair are the ones like this, when it's just a split second occurrence that catches you completely off guard.
Had this kind of thing happen several times in school, where I'd be walking or sitting behind a girl with long hair and it would inadvertantly swish against my hands or arms or wherever.
Most memorable time that happened, I was sitting behind this girl with waist length straight and THICK blonde hair at an assembly. Someone behind us yelled to her, she turned her head and whipped me in the face with that glorious silk.
She was all apologetic and we kinda laughed it off, but on the inside...whew. I was desperately trying not to lose my cool!