ACTUALLY ....
I kept my horses at a boarding stable just off Victoria in East Highland for years. I was VERY much into trail riding and would meander around in the foothills a lot. I recall a couple of instances of wandering across rather large buildings set way back in the hills.
One of them DID particularly look like a multi story hospital or hotel - made out of cement. It was abandoned and I never saw anything more than a dirt road leading up to it. It has easily been 20 years since I was back in that area but I do recall it being behind the first set of high hills to the West of Victoria. We would ride up the road past Patton Hospital and into the hills. At some point we would turn left and follow a series of trails and had come across it several times. There is actually a lot of 'flat' territory behind those hills. It would really surprise you.
Now I can't recall the Orange Grove thing as the groves have been dissappearing over the years. I do remember somewhere along the way there being a Eucalyptus grove. There was another place way to the east up beyond Shadow Hills Equestrian Center that sort of resembled an abandoned hotel or hospital. It was small, 2 story and made of crumbling cement. I imagine that all of the building up there, those places may not even exist anymore but I DO recall the two buildings so there is a very good possiblity one of them was 'it'.
We stayed away from both places as they were equally delapitaded and we didn't want to hurt the horses. If I had equine access to the hills and a few days to reaquaint myself I could probably find the one at the end of Victoria quite easily. I did not realize it was haunted other than the place gave me the willies whenever I got close to it. As a horse back rider, I learned quickly that you avoid structures that strange people may be hiding in. Especially in the East Highland area.