I use batiks all the time (have never prewashed) and have never had anything like that happen. Just wondering what type of needle you were using? A lot of people use a "Universal" which is a combination of a ball point and a sharp, I have had really good luck using a "sharp" needle when sewing. The batiks are closer woven than standard quilting cottons (higher thread count). I'm not saying this was the issue but wanted to throw it out there.