Your battery drain is (also) when the vehicle is switched off, so I'd be looking for anything using power on an unswitched circuit. E.g. the top 12V outlet in the dash above the ashtray and bottom outlet. The top outlet is unswitched - it's good for charging mobile phones. There could be a short there, or the PO has used the power feed there for something else (fitted or removed) with a wire now grouding...