Seems like someone else got the access of your freebitco account. Then he/she found those FUN tokens and sold them. Finally placed a bet with whole amount and loss the bet. As a result there is no token left in your account and your balance disappeared. The thing happened with you was unfortunate. I think freebitco can't help you out from this situation. Maybe there was no error from the site.

Freebitco shows a message template to enable 2fa authentication while a user have higher balance in his account. You should have enabled the 2fa authentication into your account before. Only password can't make your account fully secure. You should stay careful now. Few months ago aother user shared something like that. But the hacker increased the balance of that user instead of lossing them by placing bets. Chek his post HERE