A rogue ninja attracts much less attention than a former Sannin who successfully killed a major village's leader. Taro was just used to kidnap children for experiments. I think they'll come to find out that none of the experiments had gone through yet, since Orochimaru did not arrive yet. Kabuto was coming to check on their investment, which is when he encounters Kakashi and Sakura destroying that operation. Taro wasn't the smartest, but he was strong enough to watch a bunch of children--or so they thought. 

Chakra Spirit Gun. We are [i]SO[/i] original xD!