Ebay selling my missing amplifier

No they don't. I shipped a speaker by FedEx and it disappeared. They contract third party companies to make deliveries and the only "proof of delivery" is a piece of paper that says Delivered. No accountability, no investigation, no payout. 

The paper said Delivered. End of claim. 

FedEx and UPS don't operate the same way. UPS has its employees handling your package from beginning to end. FedEx contracts with 3rd party companies for local delivery. Those employees are directly responsible to their company, not FedEx. They just show FedEx a paper receipt saying something was delivered, especially in rural areas.

But FedEx has no direct way to interact with the delivery driver to trace your package. If the driver says they delivered it, end of story. You have to deal with the person you sent it to.