A myth. There aren't any "lost Christian gospels."
God moved Christ's apostles and their attendants to record and to finish His word (John 16:12-13; 1 Corinthians 13:8-10; Hebrews 1:1-2; 2:1-4). The church received and acknowledged that Word.
If the apostles didn't author or sponsor it, and the church didn't acknowledge it, at best it may be a peripheral and helpful writing (like Augustine's Confessions, or Calvin's Institutes), but it isn't a "Christian gospel" -- as if it's fundamentally going to change the image of Jesus we have from the existing, abundantly-attested records.
Dan
Biblical Christianity BLOG
How to Make Your Very Own Jesus
These are garbage dumps, not library caches. If the mss were in the garbage, there must have been a good reason. Before the days of Gutenberg and automated binderies, scrolls were not trashed like today's paperbacks.
The latest volume includes details of fragments showing third- and fourth-century versions of the Book of Revelations.
Even the greenest of writers should have known that there is no such book as "Revelations." So much for the credibility of any aspect of this article.
Intriguingly, the number assigned to "the Beast" of Revelations isn't the usual 666, but 616.
Equally revealing is the author's ignorance of the variant "616," which is no recent discovery.