No it is extremely unlikely this is an "escape". This would be lucky to survive for a week in Europe. Almost certainly what happened is someone bought one and then realized they are too complicated to take care of and decided to dump it in a spot they thought looked pretty
Also there are 1,000 of these in the wild but there are over a million of them in captivity. You can get a typical morph for about $50.
It's this, for sure. An axolotl is not going to live in the wild. I own a home near a public pond. There are pretty much always fancy goldfish swimming in it during the time of the year that everyone moves out. People just decide not to keep their fish.