That's not a good enough answer. He keeps watching Allison for a flicker; any sign that she's intentionally leaving something out. Now that he's aware of the holes in his memory, he isn't sure what he trusts. Vanya is just another name to him, one that he has to keep repeating to himself so he doesn't forget again, but he can't believe that if she was in their family he would have let her go without a fight. Allison might be suggesting they're alive just to keep him from doing something desperate.

There's a possibility that it wasn't a random accident, and someone knew exactly what they were doing by targeting what he cares about most. Either they were trying to prevent him from doing something, or they were hoping to send him away and didn't think anyone would come around to fill him in. Unless there's something more serious going on in his brain, but he's quick to dismiss the headache and nosebleed so he can concentrate on things he can actually fix. (His nose is still dripping somewhat, but he ignores it.)

"You need to rumor me." That's the obvious solution, and he doesn't know why it took him so long to come to it. He sets down the candle and gets in a better position. "We don't know what else I'm missing, so tell me to remember everything."