Any option to get a refund on a fare difference in purchased tickets?

[cardiology]

I was looking at a one way fare for 2 weeks and no saver fare was available, I then purchased the flexi fare online. 2 days later, the saver fare appears! Is there any chance I could get a refund of the fare difference? I know that cancellation and a rebooking will be much more expensive than the actual fare difference. Credit card purchase protection doesn't seem to cover tickets.

Thanks