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.
I did think it was strange they didn't spell that out though. Maybe they thought 'Mexican' makes it clear, but it reads too easily like a species name.