Once upon a time, a girl disappeared in the middle of the night.
This would usually be a cause for concern, especially since the incident took place at no other than a school of magic. It is said that at this school of magic, the security spells are tighter than the eye of a needle. The gates are always closed, except to the few who are granted the privilege of entering and leaving, at limited occasions and with the Headmaster's permission. No wizard can step foot without the Headmaster's knowledge, and no soul can leave the castle without paying the ferryman. One cannot so much as spill ink on a library book without alerting the various angry creatures (and yes, the Hogwarts librarian) residing there.
Now there are some exceptions. Yulia Zimmerman once went missing during a Quidditch match on November 1, 1905 for exactly five hours, until a certain Professor Blumendahl had the presence of mind to check the bathrooms instead of the sky. Since then, there have been no such known incidents of missing children, magical or otherwise.
Knowing this, it is reasonable to expect that people would be quite alarmed. But you would be wrong to assume so.
The girl in question was neither particularly loved or approved of by the general populace.
The professors found her rather difficult and selfish, and terribly clever, a most obnoxious combination for a girl to exhibit. The students simply found her stuck-up and mean, and were glad to be rid of her presence.
"It's something about her kind," some would say.
"It wouldn't be so bad if she was just a blood traitor," her kin, a revered circle known as the Sacred Eight would interject. "But not even the Mudbloods like her. I suppose that leaves the owls and the house-elves, who are too stupid to do anything but carry orders and listen to anyone with food." Of their number, only Theseus Scamander had anything nice to say about her person, which was that she was a lot smarter than he ever could have imagined. Nobody else volunteered to comment on this statement.
When the girl in question disappeared, no one let out a cry. No one asked her to stay. She simply went without saying a word or letting anyone know, leaving nothing but a raven behind.