I think it sounds like a load of hooey.  Now I think that exactly how much
heat a ferret can tolerate depends in part on what sort of environment they
have been used to-- a couple of years ago on a day in the 78 degree range
but quite humid I went on a walk carrying two of my ferrets in my arms.
By 4 blocks from the house they were panting, becoming lethargic, etc.--
clearly too warm, and back home we went in a hurry.  But I kept my air
conditioned home at 77 and the humidity indoors was much lower.  It
certainly felt much cooler indoors to me!  Given the drought and extreme
heat here in D/FW the last 2 or 3 summers, I'd say survival chances are zip
even before considering food needs and predator avoidance for animals that
are domesticated and had spent a part of their lives caged and feed kibble
of some sort.
 
I think the guy is either 1) yanking your chain or 2) some family really
turned some ferrets loose and maybe this someone has seen some sort of wild
animal living in the area.  In Texas in general there are a lot of species
that an uneducated person might mistake for a ferret, some of which have
even been known to be kept as pets occasionally.  The Texas Department of
Parks & Wildlife publishes a book on Texas mammals.  The 1984 version of
this book shows distribution maps for several of these species that show
both ranges and counties in which the animal has been specifically
reported.  Tarrant county (where Keller is for those who don't know) has
at times reported:
 
Long-tailed Weasels
Mink
Black-tailed Prairie Dogs
Ringtails
Raccoons
Oppossums
Skunks (2 species)
Nutria (a type of beaver with a rat-like tail)
and so on.
 
I myself have seen beavers (not nutria type) in two places in Tarrant
county in the past five years in well developed areas.
 
If you really want to know, I suggest that you find out where exactly it is
that this guy lives and call the city of Keller departments of public works
and animal control to ask about the story.  I suspect that either no one
will have heard about this supposed incident or that you'll find the
animals relocated were NOT ferrets.  If the city indeed says they moved
critters they believe were ferrets, find out were they sent them.  It
would likely be a wildlife rehabber that you could contact to find out
what was really involved.  But I doubt you'll have to go nearly that far.
 
Debra in Fort Worth
[Posted in FML issue 3290]