Answer:
I haven't got the full thing but here's my shot
A possible theme for Professor Naismith's New Game" is "some inventions aren’t perfect at first." This is first shown in the phrase "Although Professor Naismith often had to blow his whistle and stop the game as the players broke the rules or crashed into each other," because it shows the game wasn't that well developed yet, as the professor had to blow his whistle and stop the game. This shows that the "invention" (in this case being the game) isn't perfect, because it needs constant refereeing. Another example can be found in the phrase “After we score a goal, sir,” someone ventured, “how do we get the ball back?” Professor Naismith rubbed his forehead. “I guess we’ll have to borrow the janitor’s ladder again.” This shows the the professor hasn't thought of the perfect solution on how to get a ball down after a goal is scored. This, combined with the body language of the Professor, shows that the game wasn't too perfectly thought out yet. Thus, in these two examples, we can tell that a possible theme for Professor Naismith's New Game" is "some inventions aren’t perfect at first."