I think you're not going to get a lot of love. The actual amount of the refund, based on the segments you'd already flown, was ~$30. You might be able to argue that unless they were selling a walkup fare for that segment for $30, your refund should have been higher, but it's not likely to get very far. And the $200 was already there to take care of that inconvenience for you.

Then again, I actually had a very similar situation the other day--CO went mech and was delayed 2 hours, which would have caused me to misconnect. I bought 2 WN tickets from the gate agent. It was a no-brainer, versus getting stuck in Newark for the night. I then called CO while boarding the WN flight, and after 5 minutes on hold checking on the mech delay, they agreed to refund me. Even if I hadn't gotten a full refund (and there were several extenuating circumstances which led me to believe it was a long shot) it would have been worth it.
So, I suppose you could try again and you never know...