Even if a hair exists I'm not sure what it would prove. She had just had sex an hour earlier. She was in strange positions and sitting on the floor of a house where lots of men hung out. So a hair stuck to her bottom. Big deal.
The level of evidence in this case is ridiculous. Kobe had blood on his shirt and people still didn't think he popped her. If she had a hair on her thigh and the DA proposed that was evidence of rape he would have been laughed at.
You're right. In many cases, a hair could have meaning, but how many cases involve filthy Fraternity Houses and women mopping the floor with the bodies?
It's kind of surprising she didn't dredge up more from the floor in that house.