Papyrus doesn't quite gasp, but he inhales sharply. "That's like Sans, he couldn't remember me... At all. Even when I went to check on him..."

The polite pleasantries had been better than the interrogation or the panic before Sans left, but not by much. And the complete lack of recognition... Really, Papyrus is a pretty memorable sort of person. Loud and active and pushy. For Sans to remember nothing, even when faced with his (disguised) brother...

He brightens "But you just remembered her! Even after everything they did to make you forget. So, you're getting better. And you'll keep getting better!"