Q: I upgraded to Maverick, then upgraded to latest Keynote and lost many movie clips that I had in my presentations

Possibly from a Time Machine backup ?    >  Time Machine - Frequently Asked Questions 15. How do I view or restore selected items?

http://support.apple.com/kb/HT6049 states:

Reverting documents created in the new iWork for Mac applications to the previous version’s file format

New or existing documents you open in the new versions of Pages, Numbers, and Keynote use the new unified file format. These files can’t be opened in the previous versions of the iWork applications. To revert the document file format to the previous version, you can do one of the following:

1. Documents that you haven't edited can be reverted to the iWork ’09 version by selecting File > Revert To.
2. If you have edited the document and want to preserve the edits, you can save it as an iWork ’09 document by selecting File > Export To, then choosing Pages ’09, Numbers ’09, or Keynote ’09.