If your driver completed the delivery, then the package's tracking status or a delivery notice (a UPS InfoNotice®) should indicate where your driver left the package. Shipments that don't require a signature can be left in a safe place at the driver's discretion. This could include the front porch, side door, back porch, or garage area.
If the tracking status indicates that your driver completed delivery and obtained a signature, the package might have been signed for by a neighbor or another resident at your location. If the driver delivered your shipment to an alternate location, you should have received a UPS InfoNotice that indicates where the shipment was left (for example, a neighbor's house or leasing office).
Check with others at your address, or perhaps a neighbor, to see if someone else has picked up the package. You can also check around the entrances of your residence for the package, particularly on back porches, bushes, garages, grills or other places that might protect your package from theft or weather. Note that drivers may also use plastic bags to protect your package from the weather.
If you still cannot locate the package, contact the sender of the package to initiate a trace process with UPS. The sender will then follow up with you on the progress of your shipment.