Surely if i can learn to see the dragon then its no longer invisible
Yes, it would no longer be invisible to you, but, can you prove its existence? Its still invisible to everyone else.
For a factual incident of this sort, try looking up ghosts and angels. Many people have seen them. However, most of the science community says they don't exist.
Or look up the Mandela Effect. Half of the people remember something different. How is this possible, when the past is supposed to be the past and unchanging?