Board Thread:Wiki Discussions/@comment-25349984-20140826061256/@comment-26302001-20140918222730

How else would he have found it considering Obito hid it and sealed it? Zetsu is a sensor, he found Naruto and Bee the instant they came out of the giant turtle and the barrier that was put up. I am 99% positive he used his sensor abilities to find the eye for Madara.