From the article it doesn't appear they've ever been found alive in the wild anywhere but their natural habitat. This was likely a remarkable chance happening where an owner released one and she found it within close succession or else it likely would have died very quickly.

If there is a wild population, that would be an even more amazing story.

It is absolutely an abandoned pet. They cannot survive outside the tropics. Hell, they can't even survive outside the 2 lakes in Mexico City that they're hyperadapted to

There are less than 1,000 of them in the wild. Trust me if it was possible to establish a population somewhere else outside of captivity, scientists and conservationists would already be on it