Following this ^
I believe it's officially called " The Ghost" , at least in the new survey about the characters we want to see more of in the next update, and in the wiki - altho i don't know if the wiki is curated by fans or by komisari themself.
But beside that i havent found any more events beside the one you mentioned, despite checking the whole map at midnight multiple times. I hope we don't get much "official" hints and support on this, 4th wall breaking events like this are really fun to discover by the community joined effort ! Let's see if anyone else found out more