The running, I can understand a bit; explosion happened distracting them, they assumed when he talked was his return time, and the area was too damaged to retest. The throwing though, completely their fault; not only were they not watching him, and unable to locate where/how he disposed of the...
Have they ever actually explained what all demonization does to humans? because they are certainly still themselves. At most, seems to remove all restraint from the person, in both power and desire, but even then they don't seem unhinged and can still make reason. Turning Shin into a demon...
Wouldn't Great Sage be the easiest? Just lock yourself in a room claiming its research required for your title, occasionally hand out a book of scribbles saying its the sum of some research written in code.