Yep, it's actually a dual stage system. So one or both squibs will fire depending on the severity of the impact.

But to your original question, either the ORC or one of the lateral accelerometers has failed. The squibs themselves take a lot of juice to fire. Current induced by ambient RF energy will not fire a squib under normal circumstances.

I would take AMGlover's advice and have the dealer check for DTCs. My guess is that the driver's side lateral accelerometer, possibly in conjunction with something else that was happening at the time caused the ORC to fire the airbag.