So why do CO's own fare rules state that:

A. Once you have checked in, the ticket is considered used, and

B. FARE RULES TEXT
CHANGES
CHANGES PERMITTED.
NOTE -
A. UNUSED TICKETS ARE FULLY REFUNDABLE.
B. THE UNUSED PORTION OF A PARTIALLY USED TICKET
IS REFUNDABLE TO THE ORIGINAL FORM OF PAYMENT.

What exactly is an "unused" ticket? Your explanation is not supported by CO's own fare rules. CO does not differentiate between "checked in" and "flown" - at least that I can find. I'd like to see this in black and white before assuming I can request a refund at some point after check in.