Assistance with A-z claim

Bit of advice needed please…

Just had an A-z granted as customer’s item was never received, presumed lost (or still delayed) in post. No contact at all and in his A-z he notes ‘Are there any updated tracking details for this item? I know there are Royal Mail delays but I haven’t received it yet.’ (could have just emailed me that message before filing claim but there you go).

Ok, so in the A-z email from Amazon, one of the grounds to appeal is if you arrange to send a replacement item to customer, provide the tracking number for it etc. But how would that work - he’s already received a refund, if I send a replacement out now, how does it get repaid by him/refunded to me? Is his card recharged? Do Amazon fund it? Thanks for any insight,