Harry's sources told him to look for Voldemort in Spain, in the mountains. He would not touch Voldemort. They were looking for the Horcruxes now, he stressed to Ron and Hermione again and again. If it meant fleeing from an opportunity, fine. There would be another one. They wanted the locket. For that reason only they wanted Voldemort.
They hiked for three days, then watched. With the aid of every Dark detector they could carry they tracked down Blaise and Draco, wondering if they should approach, was the locket still there. Hard to say. But if they didn't act they'd find out the hard way.