This is a paragraph from Toby's blog.
If a decklist is altered with basic lands because a player loses some cards, the change can be reverted without penalty at a later point. The player still needs to alert the judge that the change has been reverted.
This paragraph is from additional remedy section in IPG under D/DLP.
this change may be reverted at a later point if replacements for lost cards are found.
Then this paragraph is from additional remedy section in IPG under MC.
If the player is unable to find replacement cards, he or she may replace those cards with basic lands for the remainder of the tournament. If he or she chooses to do so, the decklist is changed and cannot be reverted, even if replacements are found.
Why do these situations have different approaches? They seem very similar. Perhaps it would be better to allow to revert the changes in both cases.