I used to think so, Or lets say that gambling and trading has a big difference. Gambling is no sure about money back while trading is sure in that case. Gambling is a game where you have no sure wheather you win or not. So absulotely, gambling and trading are not the same.
Yes the money back thing. Even just for a little bit that will be left those are still bitcoin. If a dump continues you can somehow withdraw and get back some of the bitcoin that is left.
Or if you have an application in your mobile phone you can set an alarm whenever there will be a dump. Just put in the number to which you think is a big lost if ever it came to that point.