Guy,
 
I have had two ferrets who started digging at carpet when they weren't
feeling well, physically.  Neither of them had been diggers before.
So you may be dealing with a medical problem rather than a behavioral
problem.  Both of mine (one has since passed away) were/are suffering
from disorders of the digestive tract.
 
I know this is anecdotal, but it may still be worth having your vet look
into.  Perhaps the emotional stress from death of Ozzy's pal caused him
to get ulcers?
 
Good luck,
Nancy and critters
[Posted in FML issue 4560]