I would go back in person to the drop off shop and ask if your parcel is still there. (Calling head office they will just tell you what normally happens, not what is actually going on here - if your parcel hasn't been scanned then head office / customer services don't know anything more than you do). Last time I used DPD, and it was and will remain the last time, my parcel was still at the drop off shop a week later because apparently the DPD van was too full to take it every day (parcel was on the larger size but still within standard DPD size). I took the parcel back.
If your parcel is still at collection shop, insist on being given it back. Then you can refund your buyer, and chase Packlink for a label refund (they've not delivered the service you paid for) - bear in mind Packlink are so useless you may have to raise a chargeback with the card provider you purchased the label with.
If your parcel really isn't there, then all you can do is wait for any tracking update, but if the INR case deadline is reached you will have to refund the buyer. Otherwise, a buyer who is chasing you will escalate it after midnight/next morning and eBay will refund at your cost and withhold final value fees.
If in the meantime the item arrives then yes you will have a problem - Packlink will close their claim, eBay will tell you that you refunded the INR voluntarily. I have heard that if you hold off issuing the refund and eBay do it for you, then you can ask eBay to later reverse that refund if tracking proves delivery and they may do that. However, I have also heard that eBay will only grant an appeal if there is evidence that eBay made the wrong decision at the time - eBay refunding when tracking showed no update wouldn't be the wrong decision, so they may refuse to do anythign. So in my view it is better to refund voluntarily, get eBay fees back.
You would then have to try to arrange return or repayment of item from buyer. Most buyers should be cooperative if you offer return at your cost or a repayment minus something for their inconvenience. If not, you could as a last resort threaten them with a small claims case - they should not reasonably keep the item if they didn't pay for it.
Had you purchased the label directly from DPD you could also potentially get in contact with them and ask for the item to be redirected back to you if found again. However, as you purchased the label from Packlink the DPD phoneline will hang up on you, so I'm not sure if you can do that in this case.
Personally, I would not use Packlink for items of any significant value because involving another third party makes resolving any issues like this even more difficult.
