Slight Mishap

So there was a slight issue on the ole RC Airplane last night. I had it out in the back alley trying to trim out the engine. Normally to do this you hold the plane between your feet and you run up the engine to full power. Then you can turn this little mixture knob that is located about 1 inch from the propeller to set it for optimum performance. Keep in mind that this engine at power runs at about 15,000 rpm. So I get the thing started and everything seems normal. What I didn't realize is that during the start, the prop nut/nose cone came off in the starter cone. Not two minutes prior I had tightened this nut so I'm sure it was tight. Well needless to say I had no idea this had happen so I continued with my trim run. With the engine at full throttle, my hand a mere ass hair from the prop and my face someplace in the plane of rotation I'm sure, the prop retaining washer came off which let the prop turn free and come off. The washer went flying off into the field behind our house. The prop came off and luckily bounced off the ground prior to it coming directly at my face. Good thing it scrubbed off a little speed, cuz it was hauling ass. Of course at this point there is no resistance on the engine since the prop is no long there pushing any air. Now that 15,000 rpm is upwards of I'd guess 18,000 - 20,000. I'm pretty sure I bounced the piston off the top of the cylinder. I'll have to break it down and take a look tonight. I was luckily able to get it started again after a quick refuel and a new glow plug but I still wanna check it out. I do enough dead stick landings on my own, I don't need any more caused by engine failure.