Where is the Parchment?

In his book "The Road to Santiago" (University of California Press 1957) Walter Starkie writes the following about a document found in 814 with the body of Saint James by Bishop Theodomir. Does anyone know more about this parchment paper and what it said?

"Theodomir, by divine revelation after much fasting and prayer or, as the tradition goes, by the discovery of a piece of parchment or papyrus near the body in the sarcophagus, convinced himself that there lay the body of Santiago, Son of Zebedee."

It a footnote, Starkie writes that "nothing whatever was said about the document until it was mentioned in the Chronicon Irense in the twelfth century, three hundred years after the revelation of the body."

Here is the logic about the document. If it supported the finding that it was Saint James buried there, then Theodomir would had made it public as proof, beyond and in addition to, the miracles that were asserted. (As well as the divine revelations)

But he did not. So why was that? If the document pointed to someone else, like Priscillian who was also beheaded and buried in Galicia at the end of the 4th century, then Bishop Theodomir could have been motivated to hide the document if he was swept away by the magnitude of the mythology and the prospect of his elevation in the church hierarchy by having the Apostle's remains discovered in his backyard. In the 9th century, the status of churches and their leaders were measured in direct proportion to the relics they possessed. For Bishop Theodomir it was like hitting the lottery!

The other explanation was that the "parchment or papyrus" was something added later in the twelfth century, as history was rewritten and expanded by the church. It never existed in the first place. The inexact description (what exactly was the document actually written on - for James it might have been papyrus, but for Priscillian it would had been parchment) would then lead credence to a revisionist explanation.

The whole thing has my head spinning - Does any one have an opinion? Did this alleged document ever even exist or was it a later invention?