When it has happened? The domain name you added to the post has been placed for sale. When I click the link this was popped to me.
The owner of slushcoin.com is offering it for sale for an asking price of 795 USD!
Isn't surprising the owner asking only for $795 to hand over the domain? Any site that asks you to make a fresh deposit and upgrade plan for withdrawing your fund is definitely a scam. This isn't new in the internet world. Just don't be greedy.