Hello there, well, It isn't a bug, It is your own fault that you didn't pay attention to the switched rules, When you duel someone and click "accept" you have to make sure that you are aware of the rules, for that reason we have a 2nd tab which helps you to check the rules clearly again, in this case the results will be bad because it is your own fault, so your items won't be refunded though.
Anyways, Submit a ticket in the helpdesk -
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