Vacant Lots Disappear

Have discovered that if I try to put a sim, house, or community lote into a vacant lot the symbols disappear once I have the selected entity clicked and on the mouse. This happens whether am in the game or create a world. It's been a few years since I last tried so don't remember if this is a glitch, there is an unpublished methond I don;t know about, or am goofing up.

Thanx in advance for your advice and counsel.