I would leave it in place. Get some clear epoxy and coat the area to preserve the floor and the build sheet. If you have a very good digital camera I would take some close-ups and then print out the "build sheet" so you can have a copy of it. On the 71 Cuda I just had we found one and a quarter build sheets, as well as a shredded mouse house in the headliner with little pieces of build sheet.
Check: Behind the seatbacks on the seats, under the seats, above the glove box, in the headliner, and both parts of the rear seat. We found the best on on the back of the rear seat. Good Luck!