I have a plan that may not be foolproof, however I believe it may be the most advantageous plan so far. Knowing that there will be a third party trying to destroy your message and implant a new one you would first have to make a decoy for him to find and destroy or edit. The next step would to cut yourself on your inner thigh to the point that once you wake up it will discomfort you enough to investigate the wound. I unfortunately did not save the link to it but I found a special ink online that will disappear after the first writing and reappear after a 24 hour period. Using the ink, write a note explaining the situation. I think most people would believe the hidden message on your thigh in your own handing writing then what some third party told you or a forged letter they made pretending to be you. If I have any holes in my plan please let me know.