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
Examples in the wild are - bar the possibility of an albino example - all dark skinned. The pink/light skinned ones are the results of mutations and ultimately selective breeding in the pet population.
So is it likely this one merely escaped? I find it hard to believe someone who would own one of these would not be an enthusiast, and that enthusiasts wouldn't find another owner for a critically endangered species rather than merely drop it under a local bridge.
> It is absolutely an abandoned pet.
That. Or the family fabricated the story for online fame.
Not saying that i have any evidence either way. Fundamentaly it is an unverifiable feel-good story with great online “viral” potential. It might be a very lucky axolotl who got abandoned, found and re-captured in the short window it could survive in the wild. It can also be a viral content strategy capturing eyeballs. In my, admitedly very jaded, guestimate I would give the two options about equal chances.