When shown from the outside, the entrance to the Vandervorts' ranch is perpendicular to the two windows on the front of the house; however, when Ben follows Mrs. Vandervort into the house, from the inside the entrance is along the same wall/angle as the two windows.
When Hoss regains his memory, he doesn't show any confusion as to how he got there. His last memory should've been the ambush, or at least leaving on the road trip before he was ambushed. And, after regaining his memory, no one told him what happened to him and who the Vandervorts were. At this point, there's no reason not to tell him.