Assuming this occured in wss3 or MOSS2007 (not sure it is the same in 2010), have the user  go to the affected site, click on thier name at the top and select "Reset Page content". Click on "OK" when prompted with a message like "You are about to reset all personalized Web Parts....." This should set the page back to the default view.

If end  users have a page edit access  then they can Edit Page -> Click on "Add webpart " on any zone. On "Add WebParts" window towards bottom click on Advanced webparts link. This will open up a toolpane on right. The top section will have your closed  webparts.

Drag and drop them onto the page.

Isha Attlee
(http://www.learningsharepoint.com/)