Walder Frey: You've lost it?

Walder Rivers: Yes, Father.

Walder Frey: It's a castle, not a bloody sheep. Presumably you still know where it is. You didn't lose Riverrun. You let the Blackfish take it from you.

Lothar Frey: He surprised us. He knows the castle better than anyone.

Walder Frey: You did lose the Blackfish after the Red Wedding. You had him right here in this hall and you let him leave. Then when I told you to hunt him down and kill him, you couldn't find him. That's what it means to lose something.