That is true. For that same reason generally searchers search in teams, so they witness each other's activities. It's entirely possible one person might have volunteered to go door to door advising landowners to seek permission from property owners along the road, while the search team (fire dept) was moving along the river bank. We don't know if the person who knocked on his door at 6:30pm was also involved in the actual search. When RL gave the information about being asked, it's important to remember that his answer was in response to a question asked of him about how he learned of the disappearance of the girls. It wasn't a discussion of what sort of search took place on his property, where, who or what so all we can do is speculate.