This would cause the aircraft to remain on the ground, not climb, as the story claims. To secure his aircraft against thieves, he inserted a gust lock into the co-pilot's control column, and padlocked it in place. This procedure is fairly common, except that the gust lock is usually placed on the pilot's control column. That way it's hard to forget it when you prepare to depart.
Many gust locks have a big red plate that hangs down to cover the ignition and master switch.
We will never know why our soon to be dead friend chose to put the gust lock on the co-pilot's side. A witness to the accident reported that he departed the runway at a very steep angle, consistent with having a gust lock installed. About this time, our erstwhile friend realized that he forgot to remove the gust lock, and that his plane will soon stall. The real problem is that the key for the padlock is on the same keyring as the key for the ignition. But he didn't make it in time.