If you've missed delivery of your UPS package the driver should leave a note on your door stating that they tried to make delivery of the package but you were not available to sign for the package.
The UPS will try and make a few more attempts before sending the package back to the sender.
If there's a local UPS store around you then maybe your package went back to that UPS store however there's no guarantee of knowing where exactly your package is and it's likely still on the UPS delivery truck anyway so that the driver can make another attempt at delivery.
If you know you're not gonna be home for the delivery then you can login to UPS.com and schedule the package to be held for you at a UPS location where you can pick the package up instead.
You'll need the tracking number of the package and the information from the note that the UPS driver left on your door.