No, you're okay, Tsavorite.
Look at the cross on the wall and lift it. You need the bullet casing to hold it in place. Once you do that, look at the wall by the door.
You have to insert something there.
Once you do, you're going to need the bullet casing again.
Oh, wait, did you get through the door? (Slaps forehead.) If not,
use the artefact. The rubbing you took has the clues you need now. Don't forget to take the artefact again when you're done.
Gil.