Although I disagree with some on the validity of this treasure, the Jesuit's were maticulous record keepers. Daily journals of their treks can be found easily in mainline libraries. Carnegie Library of Pittsburgh has the "Pennsylvania Room" where an entire section of the library is dedicated to events in Pa...including interpreted texts of the Jesuits.
Think about it for a minute. If you were traveling the mountainous, rocky, forested regions of Pennsylvania that were virtually unmapped at that point, you'd definately make references to where you were continuously so you didn't get lost. The jesuit's used astronomers to map their locations and travels, the only reliable source of direction for the late 1600's. Ancient GPS...lol. And yes, if they indeed buried a treasure, they'd surely mark it AND document it so when they returned to the area, they'd find what they left behind.
There are no big rocks in the Borie valley as the tale states. (Been there) There are LOTS of other places in Potter county along the rivers and streams that DO have rocks as big as a house. (Seen them)
Another thing to consider, when your in the thick of the woods, how easily would it be to be in a different region close by without knowing it. Your in trees with limited visibility of the surrounding areas so I would think it could be easy, with a run of cloudy days, (and you know Pennsylvania has more cloudy days than not) to be one valley over from where you thought you were when you relied on stars to guide you.
My years of research and exploration on this turned up empty. That's not to say someone with access to other documents in another area did or did not. Maybe in Canada, where the Jesuits traveled from or some place in France has a hidden archive with documents unavailable to the rest of us. I simply have my own theories of why it doesn't exist....but I have been known to be wrong before.
Al