Having searched Aubert's bunk, you will know that you need find and open Edgar and Aubert's Footlocker in the Storage room inside the Vessel. From her bunk, head back out the Northern Bulkhead. Head up the stairs to reach the deck above where Sister Aubert is.
At the top, turn to the East and then turn to the South.
Head through the next room to the South and through the door on the Southern side. This will take out of the Vessel and back into the base itself.
Head down the ramp and over to the right. Go back into the entry way, where the Decontamination Arch is. Go past the arches and through the door on the right.
Just inside this room, to the right of the door, is a bench. Go to the wall and look between it and the bench. You will find the Footlocker Key. Grab it to be directed toward the Footlocker in the storage room.
Head out of the room where you found the key, back through the arches. Go back into the sub itself. Once inside, go down either set of stairs. Turn to the East and head down the ramp there. Open the bulkhead at the end of the hall and go into the room there.
Inside, to the left of the door behind a box, you will find the Footlocker you are looking for. Inside you will find Aubert's Note.