[O]fficial: Handling Lost Cards

Note: This article was originally an excerpt from the Tardiness article which describes the philosophy behind the infraction.

It happens that upon shuffling their deck, a player realizes they are missing cards and call a judge. Reading Tardiness, this should be an immediate Game Loss, then the player has 10 minutes to find replacement, or they get a second Game Loss. However, we’ve come to realizing this was a pretty poor experience for players and that, should that happen to them again, they would likely just put a sideboard card into their Main Deck and play with it. After all, they would otherwise only get a Game Loss if they are deck checked.

Process

If a player involves you because they’re missing cards:

Away from the table, ask them whether they know which card they’re missing.
This is meant to preserve secrecy of the deck they’re playing.
If they can’t tell you immediately, ask for their name and go find their decklist.
It’s no use to hope they’ll remember eventually. Even if they identify it while you were looking for the decklist, both of you were active at the same time and this will likely have been quicker overall.
From the moment the missing cards have been identified, the player has 10 minutes to identify which card they’re missing and find a replacement copy.
They need to be back before the end of these 10 minutes, or they will be considered tardy and will have lost the match.
Note: If the cards were identified before the clock actually started, players have until 10 minutes into the round to find the replacement copy.
While the player is searching for the cards, you should find some basic lands, just in case.

Result

If they can find the replacement copy before the 10 minutes have elapsed, give this match an amount of additional time equal to the time elapsed in the round.
If they cannot find a replacement copy within 10 minutes, they can replace it by a basic land and receive a Game Loss in Game 1.
They can later remove the basic land to replace with a copy of the lost card, should they eventually find one.
If they can’t find a replacement copy and don’t want to put basic lands instead, they receive a double Game Loss.
For instance because the cards they lost are key part of a combo, e.g. Splinter Twin

Finally, note that this procedure doesn’t apply to stamped product (such as the one used during a Limited GP Day 2 or a Pro Tour). For specific procedures for losing a stamped card, read this article.