Ah, I did not mean that Hisoka planned to use us to find Lunatic for him, but rather that he planned to use us to give Lunatic incentive to emerge again. He would be greatly overestimating Lunatic's association with us if he thought that, but...it is only a theory.

As to why he would go through me, it may be that he's learned about Lunatic's dislike for the Heroes, and thought that targeting a civilian from his home world would be more effective.