None of this makes much sense, but with MP being so new, there's very little to gauge where the issue lies or originated.
If MP was not involved, my response to the buyer (at least internally) would have been "yeah, right", because in my experience, and based on the countless stories shared by others, I find instances where the buyer genuinely has no idea about a bank chargeback being initiated are the rare exceptions to the norm, however the "I don't know what's going on" is the response of buyers the vast majority of the time, because it's the only one where they "save face" yet get to wash their hands of all responsibility for what's happening.
There shouldn't be any cases on the buyer's side if it's a chargeback, however if they tried to contact you about the order, it would have had to be via a "I didn't receive it" kind of message to trigger a case somehow, even though it's well beyond the time allowed, that should also mean there's a message from the buyer attached to the case in the resolution centre, otherwise, where did that message go (and if it's nowhere, what did they say they tried to contact you about?)
Anyway, if it helps, these are the policies surrounding INR chargebacks on ebay for sellers on MP (the fee they refer to is the $22 dispute fee):
If a buyer files a payment dispute and the transaction is eligible for protection, we'll cover the amount of the dispute, and waive the fee, if the following is true for the same transaction prior to the payment dispute being received:
When a buyer reports that they haven't received their item:
An eBay Money Back Guarantee case was found in your favour, or
You refunded your buyer, or
After the payment dispute was received, you provided proof of delivery that included all of the following:
Tracking number provided by the carrier company (uploaded by the date indicated in the payment dispute notification);
A delivery status of "delivered";
Date of delivery;
Recipient's address, showing at least the city/suburb or postcode (or international equivalent) that matches the address displayed on the eBay Order details page; and
Proof of signature confirmation, if an order has a total cost (including postage and any applicable taxes) of $750 or more, uploaded as an image while contesting the payment dispute.
https://www.ebay.com.au/help/policies/selling-policies/seller-protection-policy?id=4345&st=3&pos=1&q...
