Some people should ask him to go to their home addresses.
They will leave multiple incomplete nursery rhymes (or somethings else) on colored pieces of paper in different parts of the house and then have him pick any random two without revealing any of the details yet.
Then, the resident would ask him the missing parts of the nursery rhymes, the color of the paper, and where he found it.

Important: the same missing part should be written on two different colors of paper, so if he can perfectly match both paper, color, and location for more than two instances then we have a pretty convincing case.