Henry,
 
A few months back one of our ferrets managed to pull the entire nail off
a rear paw.  As you mentioned, these things bleed like crazy and put the
critter (and humans) into a panic.  It's very difficult to sooth the
frazzled nerves of a squirming, bleeding ferret.
 
From our experience, the nail will grow back.  Holly lost hers by trying
to jump into an antique magazine rack.  The rack had small chains
between spindles and she somehow caught her nail in a chain link and was
dangling by her rear leg.  By the time my wife heard the screams and ran
in, Holly pulled herself free and was in sheer panic.  We cleaned the
site and applied antibiotic ointment, followed by wrapping with tape and
gauze.  This is no easy trick!  End result...it healed fine.
 
Good luck,
Scott
[Posted in FML issue 1043]