She paused to think about it. "Maybe you got a rare disease that makes you forget?" No, that probably wasn't it. "Or... I don't know." She frowned, feeling unhelpful. "It must be really frustrating not remembering things like that."
Other options:
no subject
She paused to think about it. "Maybe you got a rare disease that makes you forget?" No, that probably wasn't it. "Or... I don't know." She frowned, feeling unhelpful. "It must be really frustrating not remembering things like that."