Detailed Prezi is now blank. Can it be recovered?

One of my Prezis is now blank, which formerly had significant amount of content. With the exception of opening and closing the Prezi, I did nothing to the Prezi to cause this. Is there any way to go to the version of the Prezi from three days ago? The community discussions talk about reverting to an earlier version, which probably will solve my problem. However, no instructions are offered on how to revert to an earlier version. Here is the URL:

http://prezi.com/bg9pe6ef5doc/case-mk...