I feel you bro. Once one of my HDD on a raid5 array failed, so I swapped in a spare HDD(which had old stuff) and proceed to format it so it can be synced into the raid5 array. Long story short, I formatted the master HDD on the raid by mistake and the rest is history..
No point crying over spilled ice-cream, at least you have a spanking new OS (that is how i console myself but i am still crying over my lost data huhu..)