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I suppose it would be fun to discover something like that if you were a player collector. Having collected mostly non-stop since the late 70s, I have a pretty fair knowledge of what was issued, but always learning new stuff too. I don't think anyone is a complete expert on everything that has ever been made/issued. It would be incredibly difficult, likely impossible, to keep track and be aware of it all, even with the help of blogs, checklists/guides and even the internet.
That said, if you were completely oblivious to unlicensed cards before, you could find yourself uncovering a treasure trove of stuff to pick from. hopefully you approach it with caution and a reasonable expectation of prices too. A lot of it is not "worthless", any card is only worth what someone is willing to pay, but it certainly isn't valuable in most cases.
Makes me think of my 16 year old son, listening to my CDs lately and liking most. He has the chance to discover some great music and hear songs for the first time from classic artists. What a feeling!