Oh, this is one that happened when I was umpiring last season when injured.
I was at square-leg and a chest high ball got bowled at the batsman. He tried to pull it, top edged it and got caught. I signalled no-ball but no one heard me and the batsman attempted a run. When he realised he had been caught he begun to walk off, before the other umpire realised I had signalled a no-ball and called the batsman back. The fielders then tried to run the batsman out (he had only gone a short way) but missed the stumps. The opposition captain told the fielder to stop it, apologised to the batsman and let him return to his crease.
So what would have happened if the fielder had hit the stumps, and the opposition captain had been unscrupulous? Would the batsman have been out?