[At this question, Kira's confusion is souring his expression like a lemon. That's quite a big understatement isn't it? Has Makima been secretly blind the whole time and detecting all the things around her with olfaction? No... He can think of several instances that would contradict that. He doesn't understand but it seems like he just has to start explaining from the hair for whatever reason.]

It wasn't so much lost as replaced. The black hair belonged to Kosaku Kawajiri, Shinobu's husband....

[Kira shrugs. Makima already knows so much, this may as well come out.]

I may have omitted some details about her assistance in harboring me.