Harry wasn't in Godric's Hollow, and the fear of the two cousins was that when they arrived at Grimmauld Place, they would find out he had already left. Instead, hiding behind some parked cars, they saw him chatting on the sidewalk with Uncle Bill and a couple of Aurors disguised as Muggles. They acted like passersby who had met by chance, but they were actually keeping an eye on the black barrier around number twelve - invisible to the eyes of Muggles who walked by without noticing it.