On October 21, 1999, at 1400 mountain daylight time, a Beech S35, N8811M, registered to and operated by the pilot as a 14 CFR Part 91 personal flight, collapsed the landing gear on touchdown at the Roberts Ranch Airstrip, located about six miles northeast of Melstone, Montana. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the private pilot, the sole occupant, was not injured. The flight departed from Billings, Montana, about 30 minutes prior to the accident. The pilot reported that while en route to Glascow, Montana, the engine started missing. The pilot attempted to trouble-shoot the problem with no success. The pilot decided to land the aircraft and circled the Melstone area to locate the airport. The pilot was unable to find the airport at Melstone and diverted to Roberts Ranch, a private airstrip. The pilot was unsure of the airstrips condition and set-up for a short field landing. While on short final, the engine missed and the airplane descended in altitude. The altitude was insufficient for the pilot to push the nose down, so the pilot opted to try and arrest the sink rate. The airplane settled to the ground and landed hard about 25 to 50 feet short of the airstrip, collapsing the landing gear. During an engine inspection, all three propeller blades were found loose in the hub. The blade tips were curled aft with heavy chordwise scoring and leading edge gouges. The crankshaft rotated easily with compression developed in each cylinder. Spark was obtained from all top ignition leads. All of the spark plugs were removed. It was noted that the number four top, and number one bottom plugs were black with carbon. Normal operating signatures were noted to the remaining spark plugs. The fuel manifold valve screen was clean and the diaphragm was intact. The engine was then prepared for an engine run. The propeller was replaced and a fuel supply was added. The engine started on the first attempt, and the rpm was increased to 2,100 rpm. The magnetos, mixture and fuel pressure were checked. All were within normal operating parameters and the engine ran smoothly.