Why is locating an object more difficult if you start with a high power on the microscope?

When using a microscope, you are magnifying the area under the lens by however many times the magnification is on your lens. On low power the area expanded by the lens is smaller than on high magnification. When on low power more is visible and there is less area to search for your given object under the microscope. I recommend finding the object on low magnification, and then switching to high once you have found it.