Why the Joke’s on the Ministry, Not on the Muggles is an editorial appearing in the Daily Prophet (DP2).
This editorial appears on page 11 of the Prophet, and is in response to the disappearance of a London Underground tube train and would appear to be critical of the Ministry of Magic.
Unfortunately, we do not have the text of the article (DP2).
We can only speculate what the "joke" might be....
Although the date printed on the second Daily Prophet Newsletter (DP2) is 8 February 1999, the timeframe for this event is 1992-1993.
From the Web
Writing by J K Rowling on Pottermore: The Daily Prophet
Tags: disappear editorial fun illegal opinion trains underground vanish/vanishing