The ref’s place the ball at the beginning of each down, and they never noticed anything?
Exactly!
I was talking with a guy who was a retired football Ref, Texas High School ball. He said this was highly unlikely if not impossible, because Refs feel the ball between each play and after years they can tell within a few ounces and the balls are traded out to the Ballboy anytime anything out of the ordinary with a ball is seen or felt. The balls are all pressure checked by the Officials before the game and at halftime.
His other point was “just how did this deflation take place? By a player poking a needle during running with the ball?