Assuming it is a pieced quilt, I would open a small gap in a seam close by where the pin is hiding and work the darn bugger out. Then use an applique stitch to close the gap. If it is not, then can you make a small clip into the top, remove the pin and add an applique piece over the hole to camouflage the problem? If that looks too much like a booboo, then add more appliques to make it look like a planned event. Good luck.