 FAIR: While the whistle Rose grabs from the dead man is metal and  its cold and wet out, the man had only just died, which would  presumably leave him warm enough to keep the whistle from freezing  in. And once Rose starts using it, whats left of her body heat  would warm it in fairly short order (unlike, say, a fencepost, which  is too large to warm). Therefore, its reasonable that it wouldnt  freeze to her mouth either.