I replied that all the really good stuff was held onto and treasured from the first, which is why the NT really hasn't changed since it was formed. The trash was mostly thrown out, or kept only by a few people out of the mainstream. Such stuff disappeared because it wasn't of much value. Archaeology, however, loves to dig up trash (in fact, this is the main stuff we leave behind).
So out of the huge volume of stuff once written about any subject, the good stuff is faithfully recorded and passed on, and all the ephemeral or wrong stuff tends to get preserved in a haphazard fashion. Which means, you shouldn't worry too much about this "earth-shattering" discovery, because it isn't one. It's just more substandard material that wasn't worth much then, and isn't worth much now, except as a curiosity.