Was the shipment relatively local? (ie: not cross country?)
I looked at where you are and where the USPS tracking indicates the pkg is and it is totally local. Either you mistakenly dropped it in a USPS blue dropbox, your campus has some sort of mixed generic dropboxes, and/or what I speculate below occurred:
FedEx might sometimes pass fairly local shipments directly to USPS instead of processing them through their network, depending on the details of their contract with USPS and local agreements.
It makes logistical sense to not process a pkg through the FedEx Ground network, load it on a FedEx truck, drive it 200 miles, process it through that sort center, load it on a pallet, and deliver it to USPS for last mile Parcel Select delivery. Instead, I suspect they just load it on a pallet and deliver it to the local USPS dist center and let the whole 200 mile journey be last mile delivery. (Again, depends on the contract between USPS and FedEx, and local agreements for handling).
All speculation, no documentation, but fits with observations about fringe cases with Smartpost handling such as USPS just going ahead and handling Smartpost shipments mistakenly given to them at the start that they themselves truck cross country instead of redirecting to FedEx for the initial haul.
