That breed is quite literally on the brink of extinction and originates in Germany. They're one of the Old German Working Dogs, and there are only about 3,000 individuals in that
whole group in their own home country (
http://www.g-e-h.de/index.php/rassebeschreibungen/46-hunde/351-altdeutscher-huetehund). The chances a shelter picked one up in the US is unlikely enough, let alone her sitting there long enough to be adopted out without her owner or breeder claiming her. People involved in breeding and keeping rare breeds - especially ones like this where almost every individual is going to be genetically valuable to preserving the breed - are extremely devoted to keeping track of the dogs, and when one goes missing or winds up in a shelter, people know and act quickly.
I'd absolutely believe a German Shepherd mix with something fluffier - like a Golden or collie of some sort - or a longhaired German Shepherd mix. It's just statistically way more likely. I own a rarer breed myself (though not nearly as small in number as the Fuchs), and I can't tell you how many people think he looks just like their mixed breed dog!
