I have Library of Leng in play. I cast Thirst for Knowledge. Can I discard an artifact and put it on top of my library instead?

A friend asked me about this and I was not sure about the answer. I think the answer is “no I can't” because the game can't “see” that the discarded card actually is an artifact. He also asked, that if a Judge would confirm that the discarded card would actually be an artifact, would it be possible to put just one card on top of library. I said no, because of the reason above.

Nope, you cannot. The game can't see that the card you discarded was an artifact card, so you can't choose to discard an artifact card and then put it on top of your library with the Library of Leng. You either need to not apply the Library and let the artifact card go to the graveyard, or choose the option of discarding two cards (and you can put one or both on top of your library if you want). Calling a judge to verify the identity of the card does not work - that is not the purpose of a judge in a tournament, and the game still cannot verify the identity of the card, even if an outside source could.

Nathan Long
Wizards.Com Boards NetRep