Ultimately all communications on the internet are public like a blockchain in some sense (just look at shodan) but if you do not want people to know what you are doing you can use RSA cryptography os something similar and then people will not know what you are saying but they will know the approximate length of the message (depending on algorithm used)

It is not your fault, so do not say sorry, the author of this post should have said that to everyone beforehand that this is not actually private (as even memos say that they are public to everyone)