The book is called 100 Days (Plus 1).
Found it on
Amazon. You can "Look Inside", but it only has the first 3-4 pages. If you scroll down to the Editorial Reviews it gives you a nice summary of the book, and even says what happens when she sneezes.
"Eagerly anticipating the party celebrating the first 100 days of school (and "That is a long time to be in school"), Hannah bounces around with excitement. As part of the festivities, students are invited to bring a similar number of "little things" to share with the class. Over the course of the week, the girl carefully collects and counts out 100 buttons, some white, some mixed, some shaped like cats, and even a few shaped like diamonds. Unfortunately, on the day of the event she comes down with a cold, sneezing her neat pile of buttons into a big mess. Disappointed to have missed the party, Hannah returns to school on Monday, resolutely taking her button collection with her. Happily, the children are marking "one hundred plus one" that day, and the large orange button on her sweater makes her collection complete."
On
Google Books you can also sample the book. Unfortunately, it's the page right after she sneezes. Like, not even joking, the page right after the big two page sneeze. Much disappointment.
I'm so tempted to buy it so I can have the one thing that started it for me.
Author