One complete family file missing after installing iPhoto 11 ??

One complete family file of photo's is missing after installing iPhoto 11. Installation went smoothly, and all other files complete. Have checked thru entire photo lists, including photo list at the top. Found two photo's in that should have been in that photo list that were downloaded 2 months prior to installing iPhoto 11. I keep files of each family branch on left side iPhoto window. Only the one file is missing. ????