When you have a FedEx package held at a FedEx location for pickup the FedEx location will hold your package for you and keep it in the locker for 5 days.
On the 6th day the FedEx driver or other FedEx worker will remove the package from the locker and return it to the sender.
So if you have a package held for pickup at a FedEx location be sure that you can get the package in 5 days.