User blog comment:B214/Volume 21 info & spoilers/@comment-3965848-20160726065224/@comment-9595671-20160727011515

The only hard part I see in that is this compared to every other instance of a memory wipe, Trihexa not caring what he destroys. Unlike with Raynare where she killed Issei without damaging the enivronement and then wiping everyone's memories of her.

Trihexa most likely left physical destruction that a memory wipe wouldn't explain unless they repaired it instantly despite their injuries, and Volume 22 seems to hint that the human world doesn't know about this though. I kinda wish that they did as a way to really show a lasting effect from Trihexa's destruction.

It seems like it would a really good plot point to see how the human world reacts to the proof the supernatural does exist, especially since I have yet to find a fanfic that uses the idea.