Pictures rarely ever provide an absolute conclusion for these mystery pieces. To me, the hole looks larger than the holes added to damaged pottery. It also looks like more time was put into drilling this hole, it is beveled off on the outer edges. If not beveled, it has equal wear all the way around the hole. I can understand drilling a cooking stone or platform. As long as the strap or "string" tied to the piece isn't positioned where it will get burnt up, it would provide a means of removing the piece from fire, or hot water, with out being burned. I'm just tossing thoughts at you based on my view of the piece. Nice find!