Many thanks to @rasso and @tjkelly for their helpful solution – this worked for me!
NOTE to @iamrobertandrews and anyone else who finds this thread: THIS function as shown above (with your correct user ID and custom post type if you use CPTs) is meant to be a one-time use function – you put it in your functions.php (or a custom plugin if you have one) and then refresh any back-end admin page for it to run, then you can either remove it or comment it out until you need it again.
