Flamingo No. 492 escaped with a companion from a zoo in Wichita, Kan., in June 2005, after keepers failed to clip their feathers. It was spotted in South Texas alone almost 13 years later. Texas Parks and Wildlife (search for FlamingoFugitive to find update in May 2019)
This link will take you to the New York Times article written when the flamingo was first found in 2018. Both are worth reading.