I was flying my plane having a great time, then it sounded like my muffler got loose on my DA100. So, just before I could turn around and land, the engine changed sound, then I realized my prop came off in flight, of course I blipped the throttle a few times to make sure (didn't need to do that) . Landed safely, thank God. Question, Could the engine have gotten hurt by running it without a prop (no load what-so-ever)? Again, I just blipped it a few times probably to half throttle and back. Just asking you guys before I call DA tomorrow.