It's always good to tell the support about this kind of things, one site has paid neteller withdraw couple of times me twice I told them both times and they took the moneys back. Now after that I have got much better support service, if I email them about some problem they will fix it and once I got too little to neteller after withdraw, immidietly after I emailed them they sent rest of the money + good bonus.

As well as the site fixed me a special rakeback deal without any affiliates or other stuff, even tho im just a small time player.

And no doubt they would have found out the double credited withdraw sooner or later.