When you call back ask and if they can't tell you the exact reason, they should be able to tell you if the cause it was under the airlines control or not.

Suggest you call and cancel (or reschedule if you fly that route) rather be a no-show. If the representative is not able to do more than refund the $5.60, send an email requesting consideration to Customer Service from your rapid rewards account with the details/receipt if it was cancelled for something under the airline's control.