Granddad Is Not in that Basketball Team Picture

For years, I had assumed that my grandfather was one of the basketball players in this picture of the 1930-1931 Basco, Illinois, team. My mother and I weren't certain which one he was, but thought that because he had it, he must have been in it.

It turns out he was not in the picture, but just happened to have been given a copy of it by someone else. When the individuals in the picture were identified, he was not one of them.

Which explains why we couldn't figure out who he was in the picture.

What are you assuming?