Banning is not going to solve much. They just make a new account. What is going to solve this activity is that people do not follow links like this, to a fake account website and click on "log in".

Greed got the better of you and yeah the FC won't see a dime of that gil returned. Best thing to do there is for only the "leader" of the FC to have access to the company chest's gil.

When you get your rollback, I suggest maybe drop a good chunk of gil to the FC chest, since the fault lies in your lap. And for goodness sakes get FC leader to fix access to gil in company chest to "Leader Only"