Yup. That can happen. As a GM, it can be very challenging to make sure you follow all the rules you set for the PCs. Thats one of the reasons we both keep CoGMs and expect the players to speak up if something is wrong. After all, a GM can't improve when the players don't let him/her know something needs improvement. The problem, of course, comes when the GM either won't accept criticism, or marginalizes the problems with excuses. Its a GM challenge to not only be open for criticism, but also accept it and adapt to it when it proves to be justified. Too many GMs fail to do that. We're all for GMs keeping secrets, players don't need to know everything, but those secrets cannot be essential to the story functioning. Nor can the GM expect the players to build their stories around things they don't know. If its a GM secret, then it cannot fully affect the players' plot until it stops being one. It can still affect what the GM does, of course. Say the pointy-eared elf consistently kills all orcs but always burns the bodies of the priests after killing them and apologizing. That might seem odd to many. But then the GM might eventually reveal that the pointy-eared elf is himself/herself a high priest(ess) of the same deity. Until that unveiling comes, the players can only ask questions about why those particular bodies are burned and such. It would be natural for the players to debate why this is so. If the GM expects the players to not debate on the why, then they cannot keep the truth a secret.