This story is so PLANE-ly made up.
I, however, can truthfully claim to have found diapers on a plane. Not used ones, though. I was probably a teen when this happened: I walked into an airplane bathroom, and, while using the toilet, started reading the labels on all of the little cabinets. One was labeled "sanitary napkins". I had no idea what that meant (I understand now that it refers to feminine hygiene products), so I reached over and opened it. To my great surprise, it held a box of generic baby diapers, not far off in appearance from the Pampers of the day, except that these were all-white. In hindsight I have no idea what those were doing in there, but at the time I just assumed "sanitary napkin" was another name for diaper. Cool! But alas, I was traveling with my parents and sister, and could think of no foolproof way to take one with me. I folded it back up and returned it to the box. Drat! Foiled again!!