It's been hiding in the cave.
We took three Jeeps with full kit out to the plain where I'd tracked the thing. The footprints were fading, but still visible, and we followed them toward the rocky hill, where they vanished into the cave. We parked the Jeeps in a circle around the entrance and shone the headlights in. They lit the interior of the cave, and we could see shapes inside.
I went in first and Val followed. Mo stayed in his Jeep with the engine running, in case we needed to make a quick escape. We explored the cave. The roof was low, just over six feet, and the shapes we'd seen from the outside were piles of old, broken equipment: smashed water barrels, torn leather bags, smashed instruments. None of it looked recent; everything was outdated and worn.
In the centre of the cave was a pile of five disintegrating books, four larger books and a smaller one that looked like it would match the cover I'd found when the thing first came. All the books were damaged: we'd found the source of paper.
There was no sign of the thing. I tried to explore the rear of the cave, but it continued farther than the light from my torch could reach. I might go deeper another time. We carried the books out to the Jeeps, and as much of the rest as we could fit in.
We'll start sorting through it all tomorrow.