The Melbourne Cup-winning rider, who also missed the Shergar Cup at Ascot because of a virus, has been laid low with the flu.
She had previously ridden Kaspersky to finish a very creditable fifth of 16 in the Queen Anne at Royal Ascot and Chapple-Hyam was keen to resume the partnership.
"Unfortunately there's lots of flu going around in Melbourne at the moment and even I've got a bit of a head cold myself," the trainer told www.racing.com.
"So unfortunately she's (Michelle) not able to ride but we've engaged Luke Nolen.
"I met him a few years ago in Newmarket when he rode Black Caviar.
"He is more than capable, he's a multiple Group One-winning rider."