Player Card Games

This weekend, I had a single U-11 game at a local club.  The game was part of a league I only work occasionally.  It just turned out that I was available and the game was being played pretty close to my house.
When I arrived, I noticed the home club had their entire team at the field (in other words, plenty of players) while the visitors were clearly short handed.  The visitors had enough to start, but we gave them 5 minutes extra to get another player or two to the field.  They started the game with 8 (In my state, we play full sided, 11 players for U-11).  The game ended up very one-sided.  At the half, the home team was up 5-0.
The rules of the competition say players arriving after the start of the 2nd half may not enter the game.  At half time, my AR pointed out that another player had arrived at the bench, but he had yet to see a player pass for the player.  I indicated that we should keep an eye on the situation and we started the 2nd half.  About 18 minutes into the 2nd half, the coach calls for a sub.  My AR waves me over.  He points out that the coach has given him a player pass, but the picture is clearly not the player standing at halfway.  I take the player pass over to the coach.  I pointed out that all players must have a pass and that the pass in my hand clearly did not belong to the player in front of me.  He mumbled something about giving me the wrong pass etc.  He was caught and he knew it.  Extra points go to my attentive AR, a young kid.
So what's the lesson I'm trying to convey here?  I guess there are two things:  First, coaches will try to get away with anything you can imagine.  That's not to say that all coaches will try to cheat.  That is not the case.  However, there are coaches that will try to get away with cheating if they can.  Second, it is easy to try to play Mr. Nice Guy and accept this player on the field since the team is playing short.  Incidentally, this player looked way under age too.  I'm guessing he was 9 and was probably the little brother of another player.  Unfortunately, you would be in big trouble if something happened to said player.  In the court room at the civil suit, you'd be asked about checking player passes etc.  Not good.
You must pay attention to these details and take all of the rules, including the administrative ones, very seriously. I put a note in my match report regarding the incident.  I also sent an email to the assignor with details of the incident.