My first guess until Mags asked her to track Mystique. Caliban could detect & track, but I can't remember or find mention of his locating a specific one he had never met.
It's pretty esoteric and from the highly-confusing Days of Future Past AU - Rachel Summers AKA Future Phoenix, who was used as a mutant hound and could zero in on particular ones due to her psionic levels.
Of course, it could be both. No matter how you slice it, we still have "disposable custom mutie for plot device" and comic Callisto was present in name only. I can't get all AR about the comic/movie clashes and stay sane, but Storm was a much better fighter than portrayed against Callisto. I seem to remember a little issue of Morlock leadership, which I thought might be a backstory when they implied a beef existed between them in the movie pre-buzz. Then again, instead of our lovely goddess, we have Homegirl Ororo. I was waiting for her to put her hands on her hips, snap her fingers at Logan and say "nigga please" more than once.
As long as they stay consistent within the movie storyline, I'll be content. I'm just glad they didn't make Hank a teenager like they did Bobby & Cyc. <_<
