They are not present in the building hot-bar. With “K” key you can open the menu with entire list of buildings. Then you can find the autocatcher into the “Mine” section of this menu.
You can select and build the autocatcher from this menu, or you can dron it to the hot-bar (into an empty slot or replace the manual catcher).
BTW with researches you’ll discover more buildings which can be accessed only via “K” menu.
Or, you can point at the blue one and hit the U key to upgrade them if you have all the materials for it.