Luck had a seven and a half year siesta.I think Sollecito was lucky. He was lucky because Guede kept the shoe box of the trainers he wore at the time. He was lucky that his family had the resources to find a matching shoe, and to employ a forensic expert to demonstrate and justify that the shoe print did not fit Sollecito's trainers but did the trainer's from the box found in Guede's room. I think the print specialist's did not expect to be challenged. I think they looked for evidence against Sollecito and Knox and they saw what they wanted to see. They had no interest in looking carefully to exclude Sollecito's shoes from making the print.
As has been said when the police found this evidence had been disproved they hurriedly went out to find more with the second sweep of the flat when they 'found' the missing bra fastener.
Your point is very important nevertheless.