This is exactly what happened to Jitterbug about 4 months ago.  I thought
she had ECE, but the vet said it was heliobacter.  He did operate on her and
remove an enlarged lymph node and also found no cancer.  We had been
traveling accross the country and I assume she picked something up when I
let them dig in the dirt at rest stops.  She lost weight and interest in
eating very quickly.  The only difference in symptoms appears to be that
yours keeps throwing up (Jitterbug did not, but she also quit eating very
quickly).  She would not even eat "duck soup".  I learned from Joanie
Williams, a wonderful FMLer, that sometimes when they just won't eat
anything, babyfood mixed with vanilla ensure is the only thing they WILL
eat.  I used 3 tablespoons of babyfood to 2 tablespoons of Vanilla Ensure
and warmed it in the Microwave (making sure to mix it with my finger to
check for "hot" spots).  I used rice cereal, lamb, and veal babyfood with
the best results, but each ferret is different.  Some prefer chicken or
beef - they don't seem to like seafood though.  Some also will only eat the
mixture if a little ferretone is mixed in, although Jitterbug (who usually
LOVES ferratone) preferred it plain.  Babyfood is extremely mild and is
usually a very good thing to give a ferret that is having trouble keeping
food down.  I also wondered if your vet gave you the dog muscle relaxer for
the ferret or if that was your own idea.  The reason I ask is that I assume
there would be very different dosages given to the two animals due to size.
I'm glad it seems to be working, but I hope he is getting a tiny dosage.
Good luck and I hope this helps.
 
     Love and Dooks,
 
     Rebecca, Jittergbug, and Monkey
[Posted in FML issue 1836]