Vash knows that Azwel has forgotten. Has willingly forgotten what has happened. Taken the pill without complaint and Vash doesn't blame him for it. What little Vash knew of had been awful and he was sure it had been a lot worse for Azwel. It's why he isn't sure he should be discussing these things with him now. Fearful it might bring those bad memories back. Vash does not want to forget. He never wants to forget what this place does so he never looses his will to keep fighting against it.

"Oh yeah?" Vash answers and finally rolls over just a little more to peek over his shoulder at Azwel. "Some kind of secret code only mad scientists can know of?" If he was being honest he didn't exactly feel comforted by what Azwel was saying, but he did take comfort in the fact that Azwel was trying to make he feel better.