International chargeback laws may be different than regular US, however I could be wrong. You’ll need to review chargeback rules and regs for your card type (visa, Mastercard, etc) to see if they differ from US.

For instance, in the US merchants are supposed to keep records of all receipts for a certain period of time, and definitely atleast six months (though from what I remember it’s three years). Generally, your bank would process a retrieval request which is a request to the merchant for them to supply their copy of the receipt, which should be signed by you, assuming it was you using your card at the restaurant. Theres more on signatures on receipts and all that, but no reason to get into it.

Once they get the receipt to research, you get a copy as well. This allows you both to get info that could either initiate a chargeback or not, depending on what the receipt tells you. You’d be surprised how much info you can get just from a receipt. Even the hand writing can give you clues.

Since this was an over seas transactions I’m not sure if a retrieval request is possible, again I dunno if the laws are different. Call your bank again, speak to a manager that would know this.