There are two ways to find stuff in RS, that both humans and bots use. One is remembering where the object is. Everybody does this for some of the greater resources, like yew trees, magic trees, rune ore, etc. The second is searching for what your looking for, generally done when there an abundance of resource, like normal trees. Doing a search algorithm is slower then looking at just 3-4 tiles, but consider that bots would not have to search more then once. All they would have to do is have the script search the area for all the id's of whatever they want and store it in variables.