Oh I wonder if he heard fireworks and got scared? I'm glad he's wearing a tag and that usually works very well for me, can't believe the office is ever closed, the should have call forwarding, I'm sure they could get volunteers to man the phones. I do not know of the one best internet site, there are so many, here's a place that list by state and here's AZ's listings.
Arizona Pet Lost & Found Dogs, Cats, Parrots, Cockatiels, Ferrets, AZ So glad the dog found you!