You are head judge of an Ixalan sealed PPTQ. At the end of round 2, a player turns in an Adanto Vanguard in a matte black sleeve that he found it on the floor. He has no idea whose it is, and there are a couple dozen players with matte black sleeves. When you announce the card has been found, nobody comes to claim it.
During round 5, you discover its owner, Peter. Peter confirms that the card is his, but he didn’t realize it was missing. That card is registered in the “played” column on Peter’s deck list. Peter is currently in game 2 of round 5 and his deck for the current game is 40 cards.
Because we are in game 2 of the match, the Adanto Vanguard is considered to be part of his sideboard along with all other cards that he opened and is not currently playing in his presented deck. This means that no penalty will be issued based on the current game.
However, we also have to contend with the issue of the previous games in which we know he was playing without Adanto Vanguard even though it was required to be there because he had marked it in his “played” column. This is resolved by looking at the language of the IPG: “the contents of the presented deck and sideboard do not match the decklist.“ Notably, this sentence doesn’t say ”did not.” A Deck Problem can only be assigned based on the currently presented deck in a currently ongoing game. Currently, there is no infraction, so we issue no infraction.
Return Peter’s Adanto Vanguard to him. Remind him to check the play area carefully when he stands up. Issue the appropriate extension, and have the players continue their match.
Judges feel free to answer on Judge Apps!