Also - despite the repeated attempts at implying it in the article, I really don't suspect the guy is there to creep on an elderly cancer patient in her bathroom.

It sounds a lot like he's on land, which is not protected by the 4th, and he's there well within his scope of authority as granted by the state.

No trespassing signs only apply to someone there without permission. He explicitly has permission from the state. And trespassing is very clearly not "search".

Harassment? Possibly. Abuse of authority? Possibly. Illegal search? ehhh... probably not.