Alata: It seems you may have a point....
Safari Guard: I'll go so far as to say he was incarcerated in chapter 138, so very recently.
Topic: The reason I was thinking Chao would do so is mainly because this is indeed her plan. She stated several chapters ago (too many for me to cite off the top of my head), that no harm would come to Negi because of her plans. Granted she's a pretty odd character, but I doubt she was lying. I kind of assumed that because of this it would be Chao who did the rescuing, but you bring up a good set of characters who would be capable as well, particularly Hakase.
And really, now that I think about it, I think Hakase is most likely. Because of her affiliation with Chao she would have a better handle on the effects of the watch used to throw Negi into the present, and upon busting in to help him, would possibly be able to direct him back to the right continuity. Her range of accessible equipment is larger as well, though she'd require a mage or otherwise magically inclined person to help, no doubt.
[[...wow, that was a long post.....oops.]]