Closer-BK would not show as a match for Silver/Roger because the DNA that belongs to BK (his exclusive) is a different kind from the DNA obtained from the mitochondria of Silver's cell.
MtDNA is less accurate than a primary DNA match...because it is part of the equation, but not everything. It shows a common maternal ancester.
The primary DNA is obtained from something that is just yours-your hair, bone, skin cell. MtDNA can be obtained from your sister, mother, aunt, female cousin and indicates a likelihood that you are related to someone else.
So then shouldn't BK get MtDNA sample off to the National Database then?