The piece hiding under the box reminds you to examine where certainty has been resting.

The thing you are looking for is often underneath the thing you were sure about. Certainty takes up space, and whatever it is sitting on stops being searched, which is why the answer can spend an hour a few inches from your hand. It is not carelessness; it is that confidence marks some areas as already checked.

When you are stuck, move the assumptions rather than searching harder around them. Ask what you have decided is definitely not the problem, and look there first.