How did no one see the troll going into the dungeon?

When it comes to the Harry Potter series, we have a lot of questions. Like, for instance, how did the troll get into the dungeon with no one seeing him.

It has been explained that the troll got into Hogwarts when the students and staff were preoccupied but there is absolutely no way that no one saw Quirrell trying to get a troll into the dungeon.

Sure, there are plenty of instances where the Harry Potter series doesn’t make a lot of sense but this one is a bit out there. A troll just running around and it takes Quirrell announcing its presence for anyone to know?

Shouldn’t there be some kind of alarm when an unknown being is in the school? It is, after all, a school for children. It seems irresponsible. So often, people just end up in the school despite their not being allowed there and it often backfires on to Harry and his friends. So if there was some kind of alarm system, Harry and Ron wouldn’t have had to fight the troll for Hermione’s safety.

On top of that, Snape was too busy off trying to make sure the Sorcerer’s stone was safe when, again, a troll was running free throughout Hogwarts. Shouldn’t his concern be the students? (Then again, it is Snape and he is constantly worrying about his lost love of Lily Potter over anything else.)

So how exactly did it get into the school unseen? We’ll have to believe Quirrell and the professors but it doesn’t really make any sense.

What do you think? Did the troll get in without anyone noticing? Or did someone see him and Quirrell had to make them forget? Sound off in the comments below!