what kind of blocks did you make? were there alot of bias edges? batiks are generally a very tight weave-stable fabric- they don't tend to stretch much-unless cut on the bias-which gives the most stretch on any fabric.
for next time around-if you have bias edges on the outside of the quilt- before sending to the long-arm quilter it is best to run a stablizing stitch all the way around the outside edge of the quilt- this will stablize it and keep it from stretching out of shape as it is quilted- it is also a good idea to do if you have alot of seam edges on the outside of the quilt instead of straight borders (keeps the stitches from being pulled apart as it is rolled on the frame.
i did one time buy some batiks from joannes that stretched if you looked at them wrong- they were horrible to work with- and i wound up saving them for some other project-not a quilt- but normal batiks are very stable - tight weaved fabric- have you talked to the quilter-to find out what she thinks caused the problem?