I'm so sorry that you had that happen to you!!! I make a jewelry line and I got a bad chunk of solder a while back and these necklaces I make all fell apart!!! People had paid over $1000 for these pieces and they were so upset and I felt miserable!!! It just makes you wonder if everything you have made in the past will come back to bite you!!! I feel your pain!
I was able to take the bad necklaces back and replace them with new ones and I added to them so they were nicer and I wrote a note saying how sorry I was. Obviously, you didn't do this on purpose!! I like the idea about re-dying the sweater. If that isn't possible maybe you should ask if the customer can wait to get new yarn from YOU until you figure out what went wrong.
I hope it all gets resolved!!
Late at night, when the family's all asleep,
you will find me counting stitches
instead of counting sheep!
I'm on Etsy when I'm not knitting...
I'm Hartleystudio on Ravelry too!!