Duck's Key Where Can it be?

What is the purpose of this book? I guess I haven't looked at a lift-the-flap book recently other than the Berenstain Bears books, so maybe it's just the lift the flap thing. The first two sentences are Duck saying, "I've lost the key to drive my truck," and then you move a plant out of the way with a flap and there's a frog hiding behind it who says, "I've got the key, don't tell Duck." Why? He looks like he's going on a vacation. He's got a suitcase! Why is this frog hiding this dang key from him? Every page you turn, the frog is moving to a different location with the key, and Duck never finds him. He just eventually finds that his keys are in the ignition (the final place the frog puts them) and then drives off without his suitcase.

Maybe I have to have read "Duck in the Truck," the first book in the series, to understand what's going on here, but I can't figure out why this frog is just tormenting this duck. Did he do something to his parents or something like that? Is he responsible for some kind of embarrassment in the past? It's not just that he's annoying the crap out of him. He never even ends up revealing that he was the one that put Duck through this, and Duck just ends up feeling like he solved the problem on his own. It's just bizarre.

I don't understand what the point of this book is, other than just being a weird lift-the-flap book of different places that the key could be. It rhymes, but the the second half of the rhyme is hidden behind a flap. Like, "Is it underneath the mat?" "You'll have to look harder than that." I don't know. I didn't care for it.