One of the biggest problems with phantom (or hidden) objects in SecondLife is that when you want something to show up and things behind/in front of it are not visible you often end up clicking on the invisible object instead of the visible one. So here is a nifty little trick.
If you objects aren’t visible move then up/down, away from the visible object. Then once the object is set to become visible move it back into the correct location. Using something like the elevator script will work just fine, just have it activate move() once the object has been called to show up.