questioning my intelligence

I was reading to him from his favorite book, Cars and Trucks and Things That Go by Richard Scarry, at his request (demand). Normally I like to ask him where this thing is or that thing and have him point them out to me in the book. For example, today I said "where is the pickle truck?" (referring to that giant two-page-wide pickle on wheels at the top of the page spread). He stared at me and said "It's right there, Mommy, can't you see it?". What do you say to that?