I haven't been in such a situation before, and I don't even wish to get involved in any. In my history of betting, I have not won up to that among others; in fact, I even consider myself a minus to the monthly generated revenue of betting companies because I spend very little among each of my wagers, which can't even result in a big win. 
 
And if I'm in the shoes of that guy, I will definitely do whatever I consider necessary in order to get back access to my account and withdraw that money. Sharing the story on social media will only be my first step; the next step will be to write to whatever regulatory body gave them the license to come and look into the matter.