Hempel's paradox

A quick note on Hempel's paradox (if this is what it is):

• If I open my wardrobe and see a white shoe, this is not much of a confirmation of the sentence p = "All ravens are black".
• If, however, I see in the middle of a bunch of ravens a white object that looks bird-shaped and, after further inspection, it turns out to be a shoe (rather than a raven), then there is substantial confirmation (or lack of infirmation?) of p, probably much stronger than simply observing another black raven nearby. [Is it correct to split the observation into the two steps and take the first as some sort of "prior" for the second?]

I'm trying to find realistic circumstances (less contrived than Good's "red herring" example, anyway) where an instance of the contrapositive of p yields more evidence for p than simply an instance of p.