“The border” has similarly been extended to cover the majority of the US population. https://en.wikipedia.org/wiki/Border_search_exception#/map/0 Yes, according the the US government warrantless border searches apply in West Virginia. (Map from here: https://en.wikipedia.org/wiki/Border_search_exception)
Further, in what way is the content of someone’s cellphone relevant at a border specifically? Inspecting luggage for cocaine at an entry point makes sense, but physical borders mean little in the face of the internet. You might as well just erase the phone before crossing the border.
If you’re expecting the Courts to bail him out, I wouldn’t hold my breath.
The gov’t can make an argument here this is like trying (and succeeding) at flushing, say, a bag of cocaine in the bathroom when you see the cops coming.
Something which the Courts also historically disapprove of, by the way.