You're right on one point-- the situation you described is a very plausible way for an accident to happen that places blame squarely on the shoulders of the non-government figure. That doesn't mean it's what actually happened, though.

I figure Cheney had one too many dry martinis before going out to play machoman with his millionaire buddies, and just got careless. But god forbid we make guns look dangerous--or Cheney look incompetent-- so we make up some cover-up story placing the blame on the other guy, and making Cheney look like a good, responsible person.