Hi Rebecca, We have designed and constructed many fleece garments over the years with different pocket constructions, this could be as easily as applying a straight stitch, onto the existing seam that has opened on the pocket bag with matching colored thread. However in order to provide best recommendation could you take a picture of the area in question? Take a picture of the inside and outside view of the jacket where the pocket is located, please indicate exact area where seam has opened in the picture with your finger or a pencil?
You could also send it into us for repair if you like at Patagonia. https://www.patagonia.com/repairs/