A huge theme in this book was that the Sidhe are titanically powerful, and we're all here wondering if some wizard stole something from a being more wise and experienced than /Mab/, who, lets remember, was running the long con this whole book. I find it far more likely that (assuming it's Mother Winter's) the staff was taken through some trickery orchestrated by a full Queen or Mother Summer, most likely the latter because of Summer's role in limiting the power of Winter upon mortals. Probably had more to do with a fae, and probably involved a bumbling wizard who didn't really know much about what was going on. Probably he/she got one of those lovely "rock and a hard place" choices. Merlin?