Well, I am not sure but this happened before:
I bought a RT SFO-LAX for a friend. He decided not to use it and it is not worth it to get a refund. He did not show for the outbound but the return segment remains in the my itinerary section until the return day. He did not try to do OLCI for the return segment though. I think if your the fare class of your flight is not a mandatory round-trip fare and the return segment remains in "my itinerary", there is a chance. I guess if you can OLCI for the return segment, it will be fine.