Cobalt 60 isn't particularly dangerous. I remember holding it in my bare hand in chemistry lab (encouraged by the teacher). Also, I'm never worried about when this stuff goes missing because it's so easy to detect to the smallest measurement - which means it's usually found quickly as was the case here.
Now if this was Cesium 137 that would be a wholly different matter
Now if this was Cesium 137 that would be a wholly different matter