It was expected that, given the operation of the Ideal Gas Law, the pressure inside the balls would rise on warm days, and that it would fall on cold days. That’s exactly what happened. As the source put it, “numerous” measurements made at halftime of games during the 2015 season generated numbers beyond the permitted range of 12.5 to 13.5 psi, with the reading showing a direct correlation between temperature and air pressure.

On cold days, pressure readings taken before the balls were moved to the field resulted in lower readings after 90 minutes of exposure to the conditions. On hot days, the pressure increased.

Indeed, it was believed that the actual numbers measured in the footballs used by the Patriots were generally consistent with the numbers that the atmospheric conditions should have generated that day. This should have resulted in a finding that, at most, the evidence was inconclusive as to whether there had been deliberate deflation on the day in question.

...So what happened to those numbers from the 2015 season? Per a source with knowledge of the situation, and as reported in Playmakers, the NFL expunged the numbers. It happened at the direct order, per the source, of NFL general counsel Jeff Pash.

Why would the league delete the numbers? It’s simple. For cold days, the numbers were too close to the actual numbers generated by the New England footballs at halftime of the playoff game against the Colts. Which means that the numbers generated at halftime of the January 2015 AFC Championship were not evidence of cheating, but of the normal operation of air pressure inside a rubber bladder when the temperature drops. Just as it was expected.

...
The numbers harvested during the 2015 season corroborated this. Which would provide a clear motivation to make those numbers go away, for good. Which is exactly what Pash ordered.

...The effort to test the operation of air pressure in footballs in the season played after the game in question (an effort the NFL had never before undertaken) resulted in numbers that were inconveniently similar to the numbers haphazardly collected in a game of “gotcha” that was instigated against the Patriots. Thus, those numbers never saw — and never will see — the light of day. The NFL made sure of that.