This may not be what caused your problem, but did you happen to press your seam allowances open? On one of my first quilt I so carefully pressed all my seam allowances very neatly open, which allowed lots of white polyester beards to sneak through on my nice dark "Roman Stripe, Amish Quilt in a Day". It turns out keeping the batting inside is one of the reasons we press seam allowances to one side.
This is not a solution for your current beard issues, of course, but for the future (I'm assuming you are a new quilter and apologize if I'm telling you something you already know!) I sought advice when I saw what was happening to my baby and all my guru could tell me at the time was that if I used my quilt and washed it that eventually it would stop happening, and it has. I took this picture recently ago and the colors are somewhat faded from sunlight and from washing, but no more beards! :-)