I have quite a bit of experience playing on other Coindice-based sites and have reason to believe this was a bug and not an intentional scam. However, if it has caused the player to lose balance when they should have won, it's obviously not a visual bug. The admin's response here fails to address the issue - the bets history he posted is irrelevant to the actual issue because it doesn't say anything regarding the history of the player's balance. If the OP is ok with this, the best way forward would be for the admin to provide a complete history of the player's bets so that the balance can be recalculated.

Also, to the OP: Was 0.1 a typo? From your explanation, the 'scammed' amount sounds like 0.01.