I emailed the website about this after I did last week's Azed (clearly NOT a carte blanche in my paper!) by Monday evening, then checked the site and found the correct grid.
Seems the printers were thrown by seeing a blank grid, thought it was a mistake, and printed another puzzle which may well be 2158! This was corrected after one edition, so some people buying the paper will have got the genuine 2157 Carte Blanche competition puzzle.
Today's Observer says next Saturday is the deadline for 2157, and the reply to my email agreed that the deadline would be extended. Presumably those of us who got a paper containing 2158 can submit a solution to a puzzle which (for everyone else) hasn't appeared yet!