Note that the appearance of your gadget and vehicle buildings will vary based on what level they are (as they change appearance based on level, and I think the guide only shows them at level 1)
If you aren't sure exactly what it is, best to put the other 2 objects in place, and then just rotate out the 3rd building until you get the white 'Spot' icon

Note also that if you are going for the achievement you'll need the golden dog - this requires 50k in the bank when you hit the volcano area
The dog itself also costs i think 80k to build.