i bet his parents kept them
You would be amazed at what my mom kept of my stuff.
I'm not surprised, especially if the "calendar" was more like a planner/journal with notes of things he did. I could see those going into a box at the end of the year, and eventually into an attic.
This would be especially likely if the son seemed like he would become somebody notable, which was apparent at an early age. I could see his proud parents keeping things that might be useful if anybody was going to write a biography about him in the future.
...and tossed out his baseball cards!
≡≡8-O
That's what I was thinking. His parents probably put everything in a box in case he ever wanted to look back at who knows what from his childhood. My parents did the same for me, not that I have much interest in most of it . . . but . . . who knows.