Oh, there is adrenal tissue.  Otherwise, she'd be dead of Addisons which
is what happens when there aren't adrenal products produced and why there
ferrets on meds to provide those.  It does NOT take much adrenal tissue
to produce adrenal products and sometimes it can be malfunctioning but
still tiny and hidden (which is one time when Lupron is useful).  We've
had a couple hidden under or entwined in vascular tissue over the years
but there are other places.
 
When both adrenals come out CLEANLY then meds are needs to supply the
missing adrenal products: typically Percorten or Florinef (Fludrocort)
with Prednisolone.
 
Adrenal products necessary for life help keep a proper sodium/potassium
ratio (which is why some are also given a little salt in food when there
is trouble getting the dosing right), and work to maintain safe enough
levels of hydration.
 
Has this ferret been on Lysodren?  Lysodren causes adrenal atrophy in
some ferrets (and has no effect on others), so it can cause ferrets to
suddenly go into life-threatening Addison's Crises.  That med is almost
never used for ferrets now due to its poor performance in them.  Use of
Lysodren is one possible explanation for what you have seen, and if it
was used, please have several repeated testings of sodium/potassium to
be safe.
 
(If a diseased one was atrophied it may have come out without knowing
during the vet's exploratory.  Even normally they are very tiny in
ferrets.)
[Posted in FML issue 4519]