Yesterday at a PTQ a player called me in between games 1 and 2 to say that he had failed to desideboard for game 1 and had therefore presented an illegal deck for game 1.

In these circumstances, what if anything is the appropriate penalty and remediation?

I think we need some more information. The most important being, when did
he notice? If he noticed during game 1 and didn't say anything we have a
bigger problem.
On Mar 10, 2013 8:59 AM, “Thomas Ralph” <forum-3301@apps.magicjudges.org>
wrote:

To the best of our knowledge he noticed for the first time whilst sideboarding.

If he actually only noticed between games, there is no problem. Just tell
him to be more careful.

Hasn't he committed a TE D/DLP infraction though? Where in the IPG does it say that the penalty is waived if the infraction isn't discovered during the game?

At the moment when you discover the problem, the player does not have an
illegal deck. He has an undifferentiated deck and sideboard with which he
is making decisions prior to game 2. At this point, you could “deck check”
him, discover that he has 70 cards in his “main deck” and it wouldn't be an
infraction. He only needs to have a legal deck and sideboard combination
between presenting his deck and the end of the game. At all other times,
the only thing you care about is that the 75 cards in his box are the same
75 he listed on his deck registration sheet.

Would you ever game loss a player if he sat down to review his match with
his opponent, and they both suddenly realize that he failed to reveal with
his Augur of Bolas during the match? Of course not. The time for catching
that problem has clearly passed. Likewise, your ability to get a D/DLP for
a game ends when that game ends. (Your ability to get caught cheating if
you knew you failed to restore your original list is not, but accidental
failure to de-side board Game Losses can't happen between games.)

Do you have a citation to the MIPG for that please? I think what you say is totally common sense, but not everything in the MIPG is common sense.

Edited Thomas Ralph (March 10, 2013 02:06:30 PM)

MIPG 3.9: “The contents of the presented deck and sideboard do not match
the decklist registered.”

There must be a “presented deck” at the time the infraction occurs. No such
thing exists between games, even if a player believes that in the past one
with a problem did exist.

What Joshua said - we have always held that, between games/matches, there can not be a D/DL error. Those only apply during games. That's true of a number of infractions. At GP:Denver, a certain L5 judge realized between games that he couldn't have legally removed those Argothian Enchantresses with Detention Sphere … and the floor judge made the right call: “Well, there's no infraction now … don't do that again, Scott!”