Revert to previously saved version

Students working in collaboration have lost their large Prezi assignment. They cannot undo because it autosaved. Is there a way to revert to a previosly saved version of a Prezi? http://prezi.com/2nfiwnphsjwj/?utm_ca...

Need to revert to a version prior to 11/11/2013 before 8:50 AM.

Please send suggestions to jcraney@plainfield.k12.in.us.

Thank you,
Jason