When there are no walls around, Sadie's I'll Get Me Goat will target buildings. If you drop Sadie in the right spot she'll charge right through the front door and disappear from sight!
Not all walls have to be gone or missing to have her target a building. It saved me once when an outhouse was on a corner island and I was running out of time. She charged across the water like a speedboat and killed it in the nick of time... I have never seen her disappear from view though
My goat is retarded and usually gets hung up in the walls even though there is a huge opening right next to her. Kind of like my Heavy Gunners do. They must be drinking the same kool aid