Bribes are not solicited for no reason. Officials require bribes in exchange for essential services: Getting your passport renewed, changing a land document, getting a particular license. In a small town where everybody knows everybody but the officials knows the most dangerous gang in the country (the police), it's downright inane to think handing him a note like this is going to put any fear into him. Whatever you were bribing the guy for will now simply not be done.
The citizen who does this morally self-righteous act will also get a nice target painted on his head. And should he choose to report the case, well, he's playing the usual game of dice that is the legal system here.
It would have been infinitely superior to make bribe-reporting a more anonymous process.