It's one thing to lose the dagger - and, don't get Rook wrong, she is pissed about losing the dagger, but at least that was... confiscated? Wherever it is, she can find it, that's what she means. 'Stealing it back' doesn't count as stealing, not really, cause she was the original owner and all that ( an argument that only holds up if you choose not to get into technicalities, in this case, but an argument nonetheless ).
But magic? How do you lose magic? It's a part of her, this... thing she was born with, an instinct. You can't steal that. ...Can you? Maybe if she were Bellara ( with her carefully crafted spells woven like intricate machinery ) or Emmrich ( who definitely paid attention during school ) she could explain why she feels no pull in her blood when she lifts a hand to the sky, why no sparks jump to her fingertips when she wills it ( and, boy, does she try to will it ), but she can't. She just knows that, too, is gone.
And yeah, she's also pretty pissed about that.
It's not as if it's just a matter of not trying hard enough to make it work again. Presently Rook stands in the meager front yard of the townhome she's been assigned to, lashing out with a... well, a stick, because she doesn't exactly have the dagger to channel her spells with, but she's always felt it was more about the action itself than the object. Maybe she was wrong? Because all the slashing and spinning and flinging she's doing isn't working one bit, and she's only aware of how stupid she must look ( it's a cooler display on a battlefield when there's lightning to go with it, okay, she swears ) when she realizes one of her... neighbors? Maybe? Has emerged from the house next door.
Her neighbor who kind of looks like a tiny horse. So that's cool.
"Oh." She should probably stop staring. "Sorry. I was just - is this stick yours? You can have it back." She lamely tosses it over into the adjacent yard. "I was... practicing something, and it was... uh, never mind. Wasn't really working out, anyway."