into thin air

you uregently need to hand in a letter.
it's 10'oclock and the place is closed for the night.
the ground floor pigeonhole is unlocked, and if you peer inside you can see a whole bunch of ignored mail.
you decide against leaving it at security for fear of being misplaced.
you push the lift button for the floor that the letter is initially addressed to, only to find the main doors securely locked.
you then head to the floor that houses the company's mailing room.
you enter the main doors and head towards the mailing room.
unfortunately you find the door locked up tight.
so you decide to slip the letter under the doorway.

you think, since the door is securely locked, it'll be safe for the night, right? and in the morning the first person to open the door will be bound to find the envelope on the floor and hand it to the addressed person, correct?

oddly enough, the letter never reached the intended recipient, even after 2 days. you would think that the envelope decided to sprout legs all by itself and make a run for it. i find it hard to believe that an envelope can just disappear into thin air, especially in the mailing room, a room dedicated to handle mass amounts of mail. i mean, where else can an envelope hide itself? how can a big A4-sized envelope disappear into thin air???

seriously.