Presumably the item was delivered to the collection point that you requested at checkout and when you went to collect it, you were told it had already been collected?
I don't see how this is possible, You need a code to get the item and Ebay only email the code to the buyer, it is not shared with the seller.
Personally, I would go back to the collection point and ask them to double check that your parcel is not actually there.
It probably is not Evri's fault - they delivered the parcel as requested. I think any 'blame' lies with the collection point.
After you have tried at the collection point, contact Ebay Customer Services. if they can't offer any help, try your payment provider.
Use the link below to get a callback from Ebay.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)