We have several options one is to let the mold grows on bread if were just hair an inanimated object it woud'n be possible to continue to grow.
A second option is to use a microscope, a stereoscopic and an optic one, in the stereoscopic we could see the mold hyphae and we could compare human hair and synthetic furr, and see differences, secondly, we can place synthetic hair on a slide, human hair in other slid and finally part of the mold (reproductive structures "hairs") in another slid, and make comparisons, meanwhile both hairs we would see just a fiber strand, in the case of mold we would see actual cells, and that is an irrefutable proof that is an actual living organism.