The airplane sustained substantial damage during a forced landing to a field after the loss of engine power during cruise. The pilot reported that he had stopped at an en route airport to refuel prior to continuing to his final destination airport. He had the lineman at the fixed base operator add 7 gallons of fuel to each wing tank for a total of 14 gallons. The pilot reported that the lineman placed the fueling ladder on his truck and the pilot went in to pay the bill. The pilot did not check the tanks or the fuel caps after the lineman had added the fuel. The pilot reported that he departed and approximately 1:05 hours of flight later, the airplane's engine stopped running. He reported the fuel indicators showed empty on the left tank, but 1/2 or better on the right tank. The fuel selector was in the BOTH position. He executed a forced landing to a soybean field, but the field was too short and the airplane became airborne again before landing hard in a field. The inspection of the airplane revealed that the right fuel door was open and the filler cap was off and dangling by the chain attached to the filler neck. A fuel stain was observed that went from the filler neck to the trailing edge of the right flap. The left and right fuel tanks were empty.