Mike,
 
Your vet was possibly right about the adrenal tumor.  The symptom you
described sure does fit it.  It is possible for them to re-grow hair.  I
suppose it is even possible for there to be a spontaneous remission,  but if
it does re-occur (which it often does) don't worry too much.  Please DO find
another vet.  From my experience, adrenal tumors are very readily operable,
and usually successfully done too.  Once the bad adrenal is removed, hair
growth and normal live span can be expected.  Your vet's comment about not
wasting your money on a vaccination seems to me to express a woeful lack of
knowledge of ferret heath and care.
 
But I'm sure you'll be getting other answers to your post, and maybe from our
very ferret knowledgable vets who join us here on the FML.
 
Dick B.
[Posted in FML issue 1200]