https://pages.ebay.com/shipping/globalshipping/buyer-tnc.htm...
Basically their interest in people continuing to use the service is the only reason they have to perform, the contract says something to the effect of: ha ha we can do nothing if we want.
Transfer of Title. Title to a GSP Item remains with your Seller until such time as the GSP Item is successfully delivered to you or your consignee, at which time title to the GSP Item shall transfer to you or your consignee. At no time do eBay (or its affiliates), Pitney Bowes (or its affiliates), or the third party logistics providers, shipping carriers, customs brokers, freight forwarders, or other subcontractors under contract with Pitney Bowes take title to a GSP Item.
Maybe you really needed the bike on the agreed-upon date.
Unless you’ve agreed to allow eBay to dispose of “unacceptable” parcels at eBay’s discretion.
That sort of sounds like selling something to eBay with extra steps. (Although obviously they should just return it, although they will probably charge return shipping.)