I'm not tech support but...

Did you look at how much gil you were carrying before withdrawing from the retainer? I'm not sure why step 5 about the total amount of money you were holding afterwards is relevant if you directly looked at how much money the retainer was holding before you started.

Did you recently follow a link from a "tell" message allegedly sending you to this forum?

If so, and you logged in on that page, you just handed gil scammers your login details.