Board Tutorial question "minefield" for Zap Wars

In the Board tutorial when I create the Minefield single piece and add the layers mask and invisibility fields and then try and run the module the Minefield is not there. But if i click there and activate it or turn it not invisible then I can see the piece and place it etc.
But when I run the ZAP WARS module that’s include in the zip file, that Minefield piece is visible (with the mine6 gif) then it turns invisible and masks the same as the other module. if I create another option in the ZAP wars module I get the same result. Of note is the fact that the properties for the ZAP WARS included module’s “minefield” properties, there is a white field at the top and the same icon that appears in the window pane for the pieces. Iv’e looked and I can find no difference for this.
So to clarify…why when I run the module is there no viewable icon at the start in the Pieces window?