It would be impossible for Ebay to check what had been delivered - that is why they have the Money Back Guarantee.
If you receive the wrong item, you have to open a return.
If you open an 'item not received' case, the seller would win it.
You open a return, state the item is 'not as described', the seller provides a label and has to refund you once they get the item back.
If this all happened recently (within 30 days of receipt of the item), you could still open a return case.
You would need to add the tracking number for the item you sent back.
As long as it shows as delivered to the seller, you should still get your refund.
"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)