i dont want to get you more paranoid , but in germany their are many undercover who likes to catch little fish . they like the game.
so from where you at im not sure if that car is waiting for a move by you , or its likely your the lucky guy knowing hes their and he doesnt know your watching him ,
a thing that came to my mind is , they knew by analyzing electrical bill coming from that location where farms dont use much electricity especially sheds.
so the new world we live in maybe alerts in such incident when a cop is drinking tea or coffee from that location , saying hmm... i need to do something to feel im a cop .
so ,,
an alternative situation is you stop by an act like a police , if you have a car , its not a criminal offense , just dont act much .. make 1 beep , get out of your car knock on hes windows , say excuse me Sir what are you doing in the middle of the road? no body informed me . you will know if hes a police or not.
if yes , then he will ask you who are you , tell him im a relative near by , and for security reasons in this location we dont want villins/gangsters around our children , so then ... you will know
if hes not a cop
or he foolled you by playing hes undercover job you can still know , get dexter pills to help your moodfantasy control.