A Mooney Acclaim (N40AU) made an emergency landing on a country road from FL210 because of an unspecified mechanical problem. The point of landing was only a handful of miles from the generously paved and well-equipped LaGrande Oregon Airport. After landing and getting some attention from the local sheriff's Department, the airplane flew to LaGrande. The next day - off to Texas. Does anyone know what happened? Oil cap come loose? Cowl screw? Door pop open? Anyone?  https://asn.flightsafety.