In fact, right in front of you.

Exploration Stage: Palace of Justice
From: Eli Montague
Description: I'm sure there are clues hidden in this blank stack of papers that lead to the missing document! It's an old piece of paper, with a tan mark and Keira's bookmark tucked in. Maybe the person who stole the document doesn't exist, and the ink just disappeared. If you have the lens of truth, you should be able to see it clearly!
Completed: Excellent. This lens brings up missing letters. It's used when someone splashed water on it and it's gone. I have seen something similar in an archive, and it is very valuable. See, I was right. The missing letters are coming up under the lens, you see! The documents weren't stolen!