So I got in a little trouble flying my drone today

I was interested in taking some shots of the sports stadiums in Philly and I did until a man from the stadium came out telling me to “bring it down.” I obliged and he asked for my ID and took a picture of my license plate (I think he thought I was going to get in the car and drive off). I gave him my ID and asked him was I not allowed to fly here. He said that it was a no fly zone and I told him that on my app it tells me if I can’t fly and I didn’t know. I shut my drone down and apologized for flying. After a while I think he realized that i was literally just a person with a drone and not a spy for an opposing team and he started to lighten up. He told me the police were coming and a report would be made. After waiting 40 minutes, the police finally came. I simply told them I was flying my drone and didn’t know I couldn’t fly it and the cop said that it was just a warning and made a report. The supervisor from the stadium told me that he has to report it to his “higher ups” but he is unsure what happens after that.
Does anybody know anything about what may happen? Also, the DJI app didn’t give me any indication that it was a no fly zone so what can I do differently next time? Also, is there anything I can do if a situation like this occurs again?