-or if i have the same username and login in an other dice site ( the admin can test it in other gambler and stole the money if it work) ,is't possible to find relation between the withdrawl made by the hacker and another dice
Yup, you join on dice/web and the admin know about all your detail, but from where he knows you have joined on that web(fortunejack) and you already deposit there then the hacker hacked your account.
If he just pick it randomly he may got empty wallet on that account That's weird.