That wasn't the case with our ferret. She would run all over the place and end up right back at her pen when it was time to sleep (which was most of the time).
Hell house cats are about as tame as they come, right? But cats turn feral after a certain amount of time without a fixed home. Hell I had a cat, since birth, that always ran off at night in Korea but would walk down the street, roof top to roof top, as I walked home from work then sit in the front door waiting for me to come in the house. When we moved to the US, he got one look at "wilderness" and disappeared, to be seen only twice more over the next year. He had clearly turned feral but, from the look of him, was no worse off.
Anecdotal? Sure, but I think we make a lot of assumptions about things that we believe without having any scientific basis to back up our beliefs. I think you'd find, if you dumped a bunch of ferrets in the wild, plenty will find their way home, others will survive just fine in the wild and make new homes, and still others will not survive. Pretty much the way it is in "the real world" already. No matter how much we try, we're not taking the "wild" completely out of any domesticated species as a whole. There will always be individuals that retain their instincts and natural capabilities. Enough to keep the species alive? That probably depends upon the species.