3D detail won't update and ignores changes

I've been going through the book Beginning 3D Game Development with Unity 4 and I'm currently attempting to put in a 3D paint detail mesh (SpottedBanana). That works fine, but any time I try to alter it by either changing its prefab or its object, nothing happens when I refresh it. I'm pretty certain I've followed everything step by step yet I can't alter this SpottedBanana's Alpha cutoff, Base Light, Amb Occlusion, Dir Occlusion, or main color in any way when placing it in the terrain menu. What am I doing wrong?