Da invisible "ghost being" (every visible mortal around you is swearing up and down, "Wasn't me!" "Don't look at me!") who "scuffed your vehicle", as Sheriff Roscoe P. Coltrane would say.
Nobody is claiming responsibility for my stove-in fenderdat occurred while I was parked in da WalMart lot; I guess it mustah been a non-physical "dentity" what did it, then.
A door wall is a sliding-glass door or patio door. The term is yet another example of banal Michigan vernacular, where in the residents latch on to company names, trademark names, marketing terms and product names from local companies. The terms become embedded in the local vocabulary and eventually become accepted as actual valid words and phrases. In this case the term comes from Wallside Windows in Taylor, MI (a large window manufacturer), where 'door wall' is their created word for sliding-glass door.
"Bob! John's gonna bring over them doorwalls from Wallsides on Tuesdee afternoon 'round two-thirty. Get 'er done!"