We hear this all the time, it's a common occurrence, where a courier deems to be a ' safe place' turns out not to be, and the parcel is stolen.
If the seller has tracking to show delivery then you cannot claim from them, or eBay as they have no control over where a parcel is left.
Yodel fobbed you off, it certainly is not eBay's fault. You can try them again perhaps getting a more understanding customer service agent, or try your home insurance see if it covers such a loss.
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