In 2013, 21 years after Theodor Seuss Geisel — a.k.a. Dr. Seuss — died, his widow was cleaning out a closet when she stumbled upon a box of her husband’s work that she had never seen before. Audrey Geisel immediately called Cathy Goldsmith, who had been the art director and designer for some of Dr. Seuss’ books at Random House. “I’ve found something that might be worth looking at,” Geisel told her.
Source: Yes, They Found It in a Box – The New York Times