Recently, while adding a new Web Part to a content rich page I noticed that the title of the Web Part instance shows [2] appended to the end. I wasn’t sure how this could be as I could see only 1 Web Part instance on the page. After some research I found that this could be from adding a Web Part to the page but not clicking Save before navigating to another page or closing the browser. This may cause performance issues with your page as this means a Web Part is hidden in the background, loading every time the page loads. Still not sure how this could happen? Let me walk you through a possible scenario:

1. Open a SharePoint Team Site in my SharePoint 2010 farm and Edit the home page.
   
2. Add a Web Part to the page. In this example, I am using Bamboo Rating Web Part.
   
3. After configuring the Web Part to meet the business need, click Save & Close.
   

   However, if you navigate away from the page or close the browser without clicking Save & Close, you will see the following message:
   

4. At this point, it is expected that you would OK.  However if you click Cancel then later navigate back to the page, the Web Part is not displayed.  Even when going into Edit Page mode, the Web Part is still not shown.

So the question is, how do you access the Web Part if it is hidden? Luckily a VERY OLD feature (dating all the way back to WSS v2/SPS 2003) called Web Part Page Maintenance page.  In this page, all Web Parts (displayed, closed or hidden) are listed.

In the Web Part Page Maintenance page, the Bamboo Rating Web Part is listed and it is marked as Open on Page even though you cannot see it.  To remove the unwanted instance, select the Web Part instance that is hiding and click Delete. Click Go Back to Web Part Page and you are done.