How do you know that the other team intentionally let that piece of paper (information, intelligence, whatever you want to call it) leak out??? Are you going to let this piece of paper suddenly change your game plan?
Coaching and teaching is about being able to get these kids to function and make decisions on their own. We try to subject them to just about every scenario possible and teach them what to do in each possible situation. There is a time when you have to sit back and let the kid perform without your input and hopefully that is before the season starts. Yes, high school coaches get paid and to them, this is looked at as a job. They equate winning as being successful. If they don't win, then they get fired. Well, from the teacher's point of view, if you don't teach them, then you have failed, you are not successful, and you should get fired. That aspect is lost a lot of the time.
Even if you knew what the signals were, your athletes still have to outperform their athletes. As a coach, you still tell the kids before every pitch what to do, don't you???..."Watch that runner on 3rd", "Get the out at first". The coach is still trying to reinforce the training but in the end, the athlete must perform to the standard that you the coach has set.
So, whether or not you have vital intelligence about the other team, if your players are not properly instructed to begin with, it does you no good. As a coach, I would look at the paper and see if it is happening during the game. I am not going to let it change my game plan and how I coach. If this paper is actually the other team's signals, you might be able to outfox them once, twice if you are lucky, before they switch to a different code. Then what are you going to do? Sure, you might be able to "Best" the other coach in outwitting him, but then, the game is now about the 2 coaches and not about the girls.
Bottom line, teach the girls the whole game. Set them up for success, not failure. Teach the rules, strategy, technique, and etiquette and then sit back and watch your girls excel.
I will get down from my soap box now before I fall down or I am pushed down.