What did the tracking say? If it said delivered then the seller wins
If it was false then you need to contact ebay and see what they say but they dont look too close at the tracking.
Top of the page under seller Help or help and contact or see the link
https://www.ebay.co.uk/help/buying/returns-refunds/appeal-ebays-decision-return-missing-item-buyers?...
If the size was on the shoes then it is wise to try and photo it
