A dog missing for four years has been reunited with its owner in Denver after it was found wandering the streets in Elgin, Illinois.

Kelly Booker says the 9-year-old dog named Lilly disappeared on July 4, 2011. He does not know if the dog got frightened by fireworks and ran away or was stolen.

The dog was rescued last month and taken to a shelter, suffering from a severe ear infection. She was identified by a microchip with her owner's contact information.

Booker says he doesn't know how Lilly wound up in Illinois. The dog wagged its tail and seemed to immediately recognize Booker when he picked her up at a cargo facility at Denver's airport Thursday.