There wasn’t a great way to add the order_id to the URL like that, so I had to hack a solution custom to the project.
I think the best solution would be to add an attribute to the shortcode to include the order_id instead of relying on the URL to have a $_GET variable storing the information.
Devs could then use the shortcode on custom pages without having to add variables to the URL, or be able to call the message on other non-order related pages:
<?php echo do_shortcode('[wc_pcr_message order_id="'. $order->get_id() . '"]') ?>