But OMSA is showing you the warning for the degraded array? Regardless, sounds like your drive needs replacing ... I'm guessing you have ordered it already for the site.  If someone onsite has reseated the drive, then the replacement should be relatively painless.
I have a T300 with a SAS 6iR. Fully updated running Windows 2003. I have OMSA 7.2 installed.  This server should have a 2 drive RAID 1 array. OpenManage says there is only one drive, there is no mention of drive two whatsoever - Not missing, failed, degraded, nothing - like it's not installed. I just had the remote office send me a picture of the server - both drives have flashing green lights.  I had them pull the second drive and reseat it, no change.  Any ideas? Thanks.
T300, 2 drive RAID1 array - second drive disappeared.