Even ignorance of the law is not permitted.
You have specifically admitted that you are traveling on the wrong route.
I am not aware as to what is "mistake" according to you.
As there is the violation, in spite of your having or not having the valid license at that time the offense is punishable.
Overlooking others by Police is not an exemption to an offender. Because many are escaping doing murders, one can not legalize saying that so and so committed a murder and so exonerate my argument is not sound.
You have committed a traffic violation and paid the penalty...that is simple and proper.