Okay. You can try clearing that hidden attribute using Diskpart. Select the appropriate volume as you did before, then enter:
attributes volume clear hidden
Detail the volume again and observe the attribute truly cleared. Then see what you've got as far as drive letter sticking. If it doesn't work you can change it back to what it was by entering:
attributes volume set hidden
I cannot guarantee it won't mess with your RAID setup, but I don't think it will as you're only messing with how the OS is viewing the RAID volume as a single entity, and not the individual drives.
I was comparing this detail with the mirrored volume and I noticed that the stripe is considered a RAID and the mirror is considered a SCSI Disk Device
I've got a SiI card added to one of my machines and can confirm. Not a RAID setup and no internal drives, as it only adds e-SATA ports for external use. An HD dock is connected with two HD drives and they both have similar descriptions.
Let us know how it goes if you decide to give it a shot!