For more on that discovery as related by the Patriarch Timonty in a Syriac letter, see this essay by John Reeves for my Old Testament Pseudepigrapha Course back in 1997: REFLECTIONS ON JEWISH APOCRYPHAL AND PSEUDEPIGRAPHICAL SURVIVALS IN MEDIEVAL NEAR EASTERN RELIGIOUS TRADITIONS. I also talk about Timothy's letter in an introductory page for my 2005 course on the Dead Sea Scrolls: Introduction to the Scrolls from the Judean Desert. As I note there, the (heretical but vastly learned) church father Origen knew of scrolls discovered "near Jericho" around 200 CE.
Earlier posts in Professor Jenkins's series on "alternative scriptures" are noted here and links.
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