> In August 2007, a Chinese man reportedly videotaped a large white animal swimming in the Yangtze. Although the animal was tentatively identified as a baiji, the presence of only one or a few animals, particularly of advanced age, is not enough to save a functionally extinct species from true extinction. The last known living baiji was Qiqi (淇淇), which died in 2002.
I think the problem is that you can never really know for sure if a species is extinct. But this is pretty sad, and I wouldn't know why anyone would want to go in an argument to prove the GP incorrect.
https://en.wikipedia.org/wiki/Chinese_paddlefish
Even today, there are dozens of videos claiming encounters with tasman tigers, that range from CGI to dogs with painted stripes.
> The last captive thylacine, later referred to as "Benjamin", was trapped in the Florentine Valley by Elias Churchill in 1933, and sent to the Hobart Zoo where it lived for three years. The thylacine died on 7 September 1936. It is believed to have died as the result of neglect—locked out of its sheltered sleeping quarters, it was exposed to a rare occurrence of extreme Tasmanian weather: extreme heat during the day and freezing temperatures at night This thylacine features in the last known motion picture footage of a living specimen: 62 seconds of black-and-white footage showing the thylacine in its enclosure in a clip taken in 1933, by naturalist David Fleay.
> After the thylacine's death the zoo expected that it would soon find a replacement, and "Benjamin"'s death was not reported on in the media at the time. Although there had been a conservation movement pressing for the thylacine's protection since 1901, driven in part by the increasing difficulty in obtaining specimens for overseas collections, political difficulties prevented any form of protection coming into force until 1936. Official protection of the species by the Tasmanian government was introduced on 10 July 1936, 59 days before the last known specimen died in captivity.
> The thylacine held the status of endangered species until the 1980s. International standards at the time stated that an animal could not be declared extinct until 50 years had passed without a confirmed record. Since no definitive proof of the thylacine's existence in the wild had been obtained for more than 50 years, it met that official criterion and was declared extinct by the International Union for Conservation of Nature in 1982 and by the Tasmanian government in 1986. The species was removed from Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 2013.
https://en.wikipedia.org/wiki/Thylacine#Extinction_in_Tasman...
350 species previous thought to be extinct are known to still exist.
https://www.nationalgeographic.com/travel/features/visit-ani...
https://en.wikipedia.org/wiki/Baiji