Are climbing roses typically grafted? If they are, is the stock plant usually another climbing rose or a bush type?

My sis purchased a climbing rose for her trellis a few years ago. Did well that summer but died over winter. (She had not kept the receipt so no chance of a return.) Later that following summer -- about midway through I think -- a little rose shoot popped up. She has no other roses so it had to have come from the original planting. It survived this past winter and currently there is a little rose "bush" 8"-12" tall. Was wondering what to expect if the plant is allowed to remain?