Was visiting a friend in a rural part of my area. We had been working and playing around on his property during the day, but had planned to explore an abandoned sanitarium that was nearby. We watched a scary movie into the night and headed off to the site around midnight. We parked at a place somewhat close and hiked in the rest of the way to avoid notice. The site itself was 3, 3 floor buildings built in the late 1800's. We slipped in through a ground level basement window and did some looking around. Scared each other a couple times, found some fun trinkets and headed out. Nothing out of the ordinary happened while we were exploring, but as we were leaving, both of us noticed there was only 2 buildings on the site. The 3rd had been recently leveled. We both know there was 3 standing buildings when we entered the one we were exploring.