ummm... arrows get broken/lost... im glad they werent 100% retrievable as it wouldnt be realistic
If you hit your target it can barely get lost.
Sure, the shaft might break, but it's not very likely in all honesty. The arrow head itself will remain intact, maybe get a little blunt, but that's no biggie.
Being able to retrieve arrows from a body, espectially when killed with a stealth shot, is incredibly realistic. But I agree it shouldn't be 100%, as it might be a bit of a gory mess if you try to remove it from deep within the organs if the head is jagged.