Identification of a short story about a short irrefutable self-evident proof that God exists that is kept secret

Question

I am trying to find a short story (about 20 - 30 pages long) I read a couple of years ago. Here is what I recall:
The central idea is that a [catholic] priest creates (and writes) a very short (about 4 pages long) proof of the existence of God just before he dies [or is killed]. The proof, besides of being very short has several special characteristics: it is written in simple language that anybody can read and understand, it convinces beyond any doubt anybody who reads it, and nobody can explain or recreate it afterwards [something in the line of "it was so obvious when I read it, but I can't recall what I read"].
There is a search for the written proof by [I think] the police and some priests.
At the end, the proof is found and finds its way to the pope, who, after reading it and making sure that there are no copies, put it in a safe so nobody reads it and the Vatican can stay in business.

Additional points:

• The nature of the proof is not revealed
• No theology involved
• I think the events take place mostly in France
• Possibly by a French author, late XXth century or early XXI
• Translated into Spanish
• The word "secret" was probably part of the title

Answer 1

This would seem to fit the bill:

A Corner of the Veil by Laurence Cossé

Paris. May 24 1999, 8.32pm: Father Bertrand Beaulieu of the venerable Society of Casuists, holds in his trembling hands six handwritten pages that prove the existence of God. Instantly, the secular and spiritual powers move to suppress the news, certain that it signifies their own demise. Source: Goodreads