Hi,
 
This is, unfortunately, not that uncommon with ferrets.  Our first male,
Mudfoot, lost one six months after we got him, under similar circumstances -
he had dragged a mop head behind the fridge, and got one of his nail snagged
by that backwards sort of hang nail, they sometimes get, and pulled it
halfway off before we could reach him to help.  Took him into the vet right
away.  They soaked his paw in something and removed the nail the rest of
the way off.
 
The vet gave us some liquid antibiotic for him, and we were told the nail
may not grow back straight, or normal looking.  But it did come back in
about 6 weeks, good as new.  Most likely Ratbert's will too, since it
appears that it was a clean break.
 
We have had this happen several other times with our other ferrets over the
years, but we were there to help, so no more lost nails, but only after
we failed to clip their nails on their proper schedule, which for our
household is every four weeks.  We also check their over their nails for
those little barbs (hang nails) that show up, usually when the humidity is
really low, or if I get one, that reminds me about them.
 
He should be fine, and don't be so hard on yourself.  These barbs can show
up at anytime, and get snagged on lots of things - why, once, we even saw
one of our ferrets walking around with a sock being dragged by one of his
paws, to which it was snagged on.  It was funny and scary at the same time,
and we had to be careful not rush over and try to grab him - which might
have spooked him into running and getting hurt.
 
Good luck with Ratbert,  (neat name, too)  :)
 
If anything can go wrong, a ferret can make it happen.
--
John and Leoda with: Mudfoot, Ollie, Zoe, Alya, Durk, and Augustus
[Posted in FML issue 2605]