The buyer paid for delivery. Perhaps they don't want the seller to just turn up at their door? You are trying to do something altruistic - but you have a label - you can post it, which is what the buyer has happily paid for.

If you don't post it - you won't have any tracking. You will get paid - but would be in 14 days. But that is providing the buyer doesn't open a claim for not delivered - which they would win as you'd have no evidence.

The unused label will get refunded but only if its buyer pays for the label. They would get refunded in 30 days.

If you offered free delivery - you can only get a refund if you complete the claim form within 14 days but you also have to show evidence of having used a tracked delivery service. As you won't have that, you can't claim.

My advice - I'd just post it.