Player Adam and Nancy are playing a game of Modern at FNM.
They call you over.
Adam says “My opponent activated a ratchet bomb with 0 counters some turns ago and I didn't put my Chalice of the Void in the Graveyard, what do we do now?
You ask both players, how they have been treating Chalice of the Void. And they both tell you that they have been treating it as if was on the Battlefield.
You ask Adam, ”Why didn't you put Chalice of the Void in the graveyard?“ He says, ”I forgot."

How do we fix this situation, according to the JAR?

Leave it be. “Some turns ago” is definitely too far back to correct, and nothing about the game state is illegal as it stands. At regular we try to fix game states where we can, but there is only so much to be done.

Alternatively, since it's Regilar, you could put the chalice in the graveyard now and carry on. Regular REL is wonderfully flexible like that

So both fixes are OK? This happened this past Friday, and I left it there. I talked to another judge and he said that I should have put it in the Graveyard. I looked in the JAR and it doesn't specifically say what to do.

I would have put it in the graveyard to get the game as close to where it should be as possible, but both ways are fine.

Originally posted by Frank Rodriguez:

they both tell you that they have been treating it as if was on the Battlefield

When both players participate in the “illusion” (the incorrect game state), I'm inclined to leave things as is. Granted, this is Regular REL, so I could be convinced to bin the Chalice…

d:^D