Amanda, it took me a while to learn this, but I always edit and renew a sold item. It is more trouble to do it that way but the number stays on google as sold unless you renew it. By renewing it, the item always has a link that the buyer can go to for an actual item you have for sale rather than something that sold a long time ago. Does that make sense?
Also, I tweet and facebook and pin on pinterest and other people send my items into cyberspace, so eventually all kinds of search engines pick up our items as we network.