Is there any way to force it to return to 'degraded' and attempt a rebuild?
You may try to update the motherboard BIOS and install the latest version of the Intel(R) Matrix Storage Manager, this can sometimes re-detect the information on the hard drives and set the RAID as degraded and not failed. This is a one in a million chance.
It is simple, failed = information lost. Degraded = can be repaired.