What is the MacGuffin in this story?

Wikipedia has an article on "MacGuffin" which begins with the following definition of the term:
In fiction, a MacGuffin (sometimes McGuffin or maguffin) is a plot device in the form of some goal, desired object, or other motivator that the protagonist pursues, often with little or no narrative explanation.
The MacGuffin in "Contents of the Dead Man's Pocket" is a sheet of paper. It is nothing but an ordinary piece of cheap yellow paper, but it is important to the protagonist because of all the notes he has scribbled on it. The MacGuffin is important in a story because it creates the conflict. The protagonist wants the MacGuffin but cannot get it because of some obstacle. It could be that a protagonist wants the MacGuffin but cannot get it because someone else wants it. In Dashiell Hammett's novel The Maltese Falcon, the MacGuffin is the statuette of a black bird which many people want. The MacGuffin brings them all together and holds them all together. It is the source of the conflict among all of them—Sam Spade, Brigid O'Shaughnessy, Caspar Gutman, and Joel Cairo.
Jack Finney takes pains to make the MacGuffin important to Tom Benecke, although it would be of no importance to anyone else in the whole wide world:
It was hard for him to understand that he actually had to abandon it—it was ridiculous—and he began to curse. Of all the papers on his desk, why did it have to be this one in particular! On four long Saturday afternoons he had stood in supermarkets counting the people who passed certain displays, and the results were scribbled on that yellow sheet. From stacks of trade publications, gone over page by page in snatched half-hours at work and during evenings at home, he had copied facts, quotations, and figures onto that sheet. And he had carried it with him to the Public Library on Fifth Avenue, where he'd spent a dozen lunch hours and early evenings adding more. All were needed to support and lend authority to his idea for a new grocery-store display method; without them his idea was a mere opinion. And there they all lay in his own improvised shorthand—countless hours of work—out there on the ledge.
Finney specifies that the notes are in Tom's "improvised shorthand" because that indicates that the single sheet could contain more condensed information than a sheet covered with ordinary handwriting. It is so important to Tom that he is willing to risk his life to retrieve it after it flies out the window of his eleventh-floor apartment. The whole story is based on this MacGuffin. In analyzing any story, it is often helpful to look for the MacGuffin. What does he want? Why can't he get it? Why do we care?
We only care about the protagonist if he wants something important, something we can easily imagine wanting ourselves. In "Contents of the Dead Man's Pocket" we can imagine wanting that yellow sheet of paper because it represents recognition, promotion, and money. We have to identify with the hero in order to get involved in the story, and we identify with him on the basis—not of who he is—but on the basis of what he wants. What he wants is his motivation, and the motivator is often a MacGuffin.