I believe that the scar was the horcrux. With all of the other horcruxes when they were destroyed the pieces of the item were still there, but no longer infected by Voldemort's soul. Because this horcrux was not smashed or sliced or broken by any of the means the other horcruxes were destroyed, i suppose that this horcrux item kept its form, but that the piece of Voldemort's soul was still vanquished from it, thus making it no longer a horcrux but a normal scar and destroying the soul... i sure hope this all made sense lol