"Are you, by chance, having a stroke?" Chara ventures, acidic as ever, because the alternative is -

If he's implying he's not realized they were simply...gone, for however long? They'd not known how long they were out, but it had to have been long enough to have witnessed some other planet, presumably. They cannot particularly say.

Did he not notice? Not care?

Is this to be their fate: forever fading from the lives of others, and leaving barely any evidence that they ever actually existed?