You are wrong. All the hair samples collected are in the forensic list of 498 physical samples found at the scene and remain in the court documentation.
From http://themurderofmeredithkercher.com/Evidence_List#Other_biological_traces
This is a good example of failure to disclose methodology used to the defence. There is no record of how Steffanoni came to the conclusion the hair was human. Nor how she identified the hair colour (actually different with individual hairs), was there a standard colour chart she referred to ? Did she have a sample of the defendants hair for comparison? Were there reference samples from the other flat mates and the boyfriend who might also have deposited hair? What we can say with certainty is since Knox is not blonde but had dyed hair the blonde hairs could not have been hers; as a competent Scientist like Steffanoni would have identified the hair as dyed.