Happened to me today while doing some straight line quilting with 12 wt thread.. I went more than 2 feet before I realized my bobbin had run out. Starting back up mid-line was not an option since there would be no easy way to disguise my stop and new start with such a thick thread. Fortunately, it was easy to pick out the stitching all the way to the beginning so I could start that line over....
Rob