DODDLE for eBay at Morrisons - uncollected item return

[pianolapiano]

I have recently attempted to used the DODDLE service for the very first time, but there's now a problem. Delivery of the item to my local Morrisons coincided with me being away for a couple of weeks, so when I called in to collected the package today, I was informed that I had missed the deadline date of April 13th and that the package had been returned to the sender accordingly. Obviously I hadn't been aware of the deadline, hence really ought to have properly acquainted myself with how it works. Anyway....

The difficulty now is that the sender has no knowedge of any return. The tracking info associated with the shipment seems to only cover delivery to the Morrisons store, but nothing beyond that, including actual collection from the store by the buyer. The seller's feedback is excellent and I have no reason at this stage to doubt his integrity. Looking at the eBay help facility, it seems to state that returns to the seller are tracked, in which case how might the seller obtain such information? As I say, the seller claims not to have received any notification of my non-collection and any subsequent return.

In anticipation of any advice, many thanks.