That's what I thought, perhaps the Aimians hided the dawnshard from either unmade or KR, the scouring happened because someone/some party tried to find the weapon but didn't know where exactly to find, so they destroyed everything in sight to look for it (and if the Aimians actually hided the dawnshard from everyone else, there was a good chance they will be accused for being involved with the enemy or something like that, thus "scour" not "tragedy").