How can someone not trace the guy back to you when you literally said you were his best friend, obviously sponsoring him since he had no identifiable remarkable background, so you're the most likely source of the expensive bomb, and went out of your way to bring someone at the same exam as your...
Can't you just send a letter or something to your concerned family?
Like, "Oh I'm alive, just lying low because since the demon king is gone, they don't need a hero anymore." or "faking my death because I don't want to get offed by the country".