Anything which flies under the radar ground clutter altitude would escape detection which is easy for a drone and cruise missile which use ground terrain radar. There are radars and technologies for detecting them which I believed are being used by the Saudis. So the question is how were these weapons successful? I'm not really sure and like you waiting for more info.
I am surprised by the lack of urgency towards responding to the attack. I was led to believe the Saudi's were prepared for responding to a Iranian attack? Something is amiss here it seems.