It's okay that naruto hasn't talked about this, but it's kind of weird he didn't even think about it for the readers. Meh.

Well, upon re-read Kushina did say she was very careful with her hair, to keep it out of sight, so if we assume she's competent that way, that explains why her captors didn't notice, but ... heh, maybe she hid them from her captors so well even the konoha nins didn't notice XD

But I really don't know what to say about the inuzuka failure then. I think my new headcanon was Minato's crush was SO STRONG he noticed she was missing first and then raced off like a mini-flash wile others were so busy getting organized so he was the first to get to her. XD