in the RAID configuration if it's an Intel I think its' Option 4 to Delete Raid configuration on all disks, do that, then re-assign your SSD's like your original config and it should come back without a re-install. but if you moved the HD to non-raid port and it still didn't come back I'd start getting a little concerned. because I have a few systems with RAID1 arrays (Mirror) and I can simply shutdown the system, pull a drive out pop it in another rig and it can be recognized.

as for the OS not crashing. this still doesn't make sense.... it would have to completely re-structure the array for adding a 3rd drive on the fly no way could it do that and not crash the OS. look at this link; RAID 0, RAID 1, RAID 5, RAID 10 Explained with Diagrams

but with 3 disks, span A/B/C across each drive... how could it not crash. I see adjusting a raid that is not the OS...

Vin