This depends how short was a ' short period of time'?
If you are still within 30 days of the item's last estimated date for delivery then you'll need to contact eBay Customer Services if you cannot find the seller, perhaps eBay removed them, and CS can open that case for you, for a refund.
I somehow think you've had the item for longer?
If so, eBay cannot help you and you could try your payment provider now for help with a refund.
@alexw4268
