when we edit the webpart we can able to dropdown options like Close,Delete.
Some times user scared what would happen if they click on delete the webpart,so they will click on close.once click on close the webpart is gone!.
It is very surpriesed how to get back the closed webpart,we can able to see the web part maintenance page by appending with ?contents =1,but it wont usefull to get back the webpart again.
Edit the page
Click on the add web part
In the top ribbon "Categories" last option "Closed Parts" click on it,we can able to see the closed web parts.Select the particular webpart and clik on Add as shown in the image below.
Now the closed web part is appearing, our problem is resolved.