ANCIENT MANUSCRIPTS (mostly fragments) have been recovered through a building project in an Egyptian monastery:

Ancient Manuscripts Found In Egyptian Monastery
Martin Bailey for The Art Newspaper (reprinted in Forbes)

A cache of manuscripts up to 1,500 years old has been discovered in a Coptic monastery in the Western Desert of Egypt. The find was made at Deir al-Surian, the Monastery of the Syrians, which already has one of the richest ancient libraries in Christendom. Set in the desert sands and virtually cut off from the outside world until recently, Deir al-Surian traces its roots back to the earliest period of Christian monasticism. Established in the 6th century, it was soon occupied by monks from Syria and Mesopotamia and is currently home to 200 Egyptian Copts.

[...]

A single completed manuscript and hundreds of fragments were found when reconstruction work was undertaken on the ancient tower, which is probably well over a millennium old. The library had originally been established there, since it was the most protected part of the monastery, but the first floor collapsed around five centuries ago, and a new wooden floor was simply inserted above. Recently the rubble of the earlier floor was removed during renovations, and curator Father Bigoul found a complete manuscript, embedded in a section of disused water pipe. (It is unclear if it was hidden there for safekeeping or got there by accident.) The parchment text has now been identified by Professor Lucas van Rompay of Duke University as a 9th-century Book of the Holy Hierothos.

A painstaking sifting of the rubble removed from the ancient tower also led to the discovery of around 600 fragments of early manuscripts. The earliest one identified, from around 500 A.D., is a single page from a hagiographical text, and this has now been linked with a manuscript in Russia. ...

It's not clear what other works might be contained in the fragments. The library itself is a treasure trove of Coptic, Arabic, Ethiopic, and Syriac manuscripts and the cataloguing and conserving of them has only just begun. Sounds like a likely place to find some Old Testament pseudepigrapha manuscripts. I hope so, anyway.

(Via Evangelical Textual Criticism.)