It doesn't really matter how many shares are officially available to be shorted. There's a lot of naked short selling taking place. Sometimes within minutes, sometimes within seconds, a person will sell short and then buy back the shares for a quick buck. They watch the charts and think they see a pattern and then act. It would take an investigation to uncover these trades, otherwise there's no tracing them.

The stock market is a battlefield day after day and it's not just the individual investor doing these things, but institutions and hedge funds front run trades and get their bids and asks in based on algorithms milliseconds before the retail investor can.