It was just a few scribbled lines saying that he loved them but he really needed to find a life for himself. That they shouldn’t worry, he’d be ok, but not to try to find him and that it would be best if they just forgot all about him.
They found the note some years later, fallen behind the radiator in his room where it had lain undisturbed.
They wondered if they had found it sooner whether it would have made any difference and concluded that it wouldn’t.