Obviously the bumper should have been priority #1, you should have cancelled or pushed back your vacation.
I'm only joking. My bumper arrived in my mailbox via USPS and no signature was required, its strange that yours was delivered via UPS. For future reference, if your not going to be home the day you are expecting a package to arrive, you can go on to UPS.com or Fedex.com and print a letter authorizing the driver to leave the package at the front door or with a neighbor, and it must be pre-signed.