I agree with Paul!
Playing something you're not prepared to play feels like facing a firing squad.
Its a horrible feeling and situation that has no positive benefit for either you or your audience.
I would attempt to cancel or replace the piece and remember this lesson, which is to never attempt playing pieces in public that are beyond your abilities.
Its a miserable situation I've been through many times when I was a kid and I sympathize completely.
Kids, unfortunately, frequently have no choice, but young adults and adults do!