All is not lost. Yet. TCN and I have conferred. I have toured outside with the torch. There is no kitten, and if he's ripped a hole in the wire, escaped and fallen off balcony wall, he'll have landed barely two floors down on neighbour's verandah. She is out.
Basically, it's not a high drop - you'd be worse off falling out of the bedroom window of a bog-standard terrace.
Will report in morning. Both TCN and I are on high alert but I'm not allowed to move much, and don't want to get so hysterical the breathing gets worse.
Bloody hell, what a night. I am VERY angry about the catproofing, it's all being redone come what may. We both checked it.