So back to this Photo………
I’m still standing by the idea of an unfinished structure that is not very old, for a couple of reasons. First if it had been completed and used there would be some type of knowledge as to what type of building it was, small church, schoolhouse, stage stop, or even house. Second if it was adobe and completed with a pitched roof that collapsed the areas in red would be gone or heavily damaged from the rafters collapsing inward and forcing the top of the walls out in a slight radius, deeper at the center of the long wall.
Since part of the front/back wall has collapsed inward any center beam to support a pitched roof would have damaged the opposing wall (green circle) and pushed that area outward. Also the far wall with the bigger windows remains intact when it should have suffered more damage from the roof collapsing along with the front wall, instead we just have a large section that fell inward with no damage to other parts of the structure.
Just think basic physics, if there was a roof on this structure that collapsed those beams and rafters have to go somewhere along with any roof material which can get quite heavy, so it’s cause and effect, quite a bit of inertia that would cause extensive damage.
As for the “Pottery Shards” it would not surprise me if they were some type of roofing tile that was on site and over time they just got broken up. Anybody who has worked with real clay roofing tiles knows how fragile they can be. Also the yellow circled area kinda bugs me, access to something under the structure?
As for age of this structure, not very old when the photo was taken. If it has completely vanished from the time this picture was taken then my guess would be adobe structure, even with people “vandalizing it” prior to the picture it shows little suffering from the elements, pretty good for adobe with no roof or protection from wind and rain and nobody taking care of it, my guess would be no more than 50 years prior to the photo and that is being generous.
Yes I have worked on adobe structures here in the Phoenix area, one was built around 1920ish, even had the old 2 wire with insulators for electricity, it had been cared for and added onto over the years but overall the structure itself even the roof were in good condition, so with care adobe can last.
So in conclusion, the structure in the photo, wherever it was or is,
IN MY OPINION, was never completed and so it just turned into a pile of dirt that washed away along with anybody knowing what it was since it was never completed.