Last year I had three awards to hawaii with DL, two via Skymiles and one via FB. Then DL changed the schedules, so a rebooking was necessary. With skymiles no problem, but FB had no seat on one of the needed flights. After a call to a supervisor, FB booked a T-Class-segment. At the airport, we added the CO# number to the flights, and no surprise, miles were credited for this segment, even the ticket was an award !