I missed scoring a base
The rules don't say anything about it, because they assume it won't happen.  Making rules for it would potentially allow people to game the system by claiming that they forgot.  I think the best way to handle it is make all players (not just the current one) responsible for ensuring that no base is ready to score.  Make a habit of going through each base as a group and counting up the power on it.  

If you still realize that you made a mistake before the end of the next turn, correct it as soon as you notice it, reversing state as needed.  If you get to the end of the next turn and then realize the mistake, just score it then.