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.