And even this won't be enough.
Why? Because Kakashi knows something about Sa? even if he is in the Root? Man, he knows Sa? is in the Root thaks to Tsunade, it was easy for him to search after knowing this. It's not as if he knew all along things about Sa?, he only searched after finding out about the fact that he was in the Root.
Kabuto is different. What reasons did he have to search about that man, weak, poor ninja? He didn't even know that Kabuto was part of the Medical Squad (Kabuto said so in the Tsunade's arc) at one point
What if the Leaf doctor was part of the Root? And that he gave Kabuto to them in order to train him?