: This paper leads them to discover that a room was built into the sanitarium that wasn't on the official public records—a room that "A" (Mona) was using to sneak in and out of the facility.
: While searching through a box of Toby’s things at the Apple Rose Grille, the girls find a blueprint for the "East Wing" of Radley. Pretty_little_liars_3x06
In the Pretty Little Liars episode "The Remains of the 'A'" (Season 3, Episode 06), the "interesting paper" most likely refers to the found by Hanna and Spencer . : This paper leads them to discover that
Here is why that specific piece of paper was so significant: Here is why that specific piece of paper
: It also deepens the mystery surrounding Toby’s mother, Marion Cavanaugh, suggesting that the "accidents" at Radley were planned or covered up long in advance.
: Spencer realizes the blueprint is dated months before the construction of that wing actually began.
Another notable paper trail in this episode involves the Hanna finds in Wilden’s car, which places him in a different location than he claimed during the time of the "remains" discovery.