IMO - your circumstance is a few and far between occurance, and although your actions made not a blind bit of difference, for the sake of etiquette its probably best to adhere to the best practice of not revealing.
A couple of reasons for this:
First, why bother? Your gaining nothing in revealing, (to your opponents), and only giving away tells of your game. Unless you were advertising
If so who are you and where do you play ??
Second, avoid the confrontation. Whilst most understand that you coud not affect the outcome, there are many a nmpty out there that will just see that as acceptable etiquette, and you could well be on the recieving end of said numpty revealling when all is not done and dusted. So in the name of improving the standard, muck and shush !
The first point should be more important to you than the second btw