This is "Throw Away Ticketing" which is illegal per the tariff rules.

CO will make you reprice - or you will need to cancel and pay the $100 rebooking fee then rebook a new itinerary at a new price. The airlines have gotten pretty strict about this. Easier to do on the return - just do not board the connection (with no checked luggage) - but overtime if a pattern developed (and CO does have snooping software) - CO could confiscate your mileage. Not a good thing to do.

You likely should try to make the effort to get out and catch the original flight.