Actually, you could drive yourself nuts sweating all the extra books of the Bible. (Maybe some already have?) I mean there are something like 22 books mentioned in the Bible that aren't in the Bible.
And then, in the Bible, we read... "As it is written" (with the quote following), and what is quoted cannot even be found ANYWHERE. (It's been a long time since DTS, but I'll try hard to remember where that is if no one else can help.)
Another issue is that there is no guarantee, or even likelihood that the pseudepigrapha that we have now aligns with the book's original form, or even that the original form doesn't teach wrong things. So tracking down those other books isn't that important.
Some Christians have went crazy with searching for truth in those books, even when they don't savor the plain truths of Scripture.
Paul quoted pagan poets on Mars Hill in Acts 17...it doesn't mean that their writings were inspired and have enduring truth. Even a broken clock is right twice a day.
Another example is the book of Enoch, which teaches that there were giants 100 feet tall. There's absolutely no archaeological proof of a being of that height, and I sincerely doubt it.
By the way there's all kinds of conspiracy theory nuts who come up with foolishness from pseudepigrapha including lizardlike aliens that are inhabiting human bodies. That sounds like the old TV series "V". I bet that's where they got their delusions and have simply forgotten its source.
Most of those books are available online here:
Pseudepigrapha, Apocrypha and Sacred Writings
The reason the books were rejected in the canon related to the soundness of their doctrine. Scripture has the tone of authority and these books do not.
By the way the canon was pretty well in place before Roman Catholicism so the claim that the RCs may have left something out is pretty silly. I don't even think they existed as we know it until about 550 AD. Before that, they were simply a boastful bishopric.