If a quilt gets wet or damp -
If a quilt gets damp/wet for any reason -
Do not leave it wadded in a heap - spread it out and air dry it if you can't get around to washing it right away.
However, all stains are easier to remove when treated as soon as possible after they happen.
If wet fabric is left in a wad or in a laundry basket - dyes can migrate - even from previously washed fabric.
This was one of my many mistakes - I am sure I will make some new ones!