The safest way is to find the original name and change it back. If you have these backed up in Time Machine, use that.
There is a way to find out by opening your Project File in a hexadecimal text editor, but I would not recommend it unless you are pretty handy with technology. If you are tech support for your family, try it. If you have to rely on your children or grandchildren for tech support, I would recommend that you just start over.
OK Here goes. Before you go any further, make a backup of your project. If you do the following, you risk totally corrupting your project.
Good hexadecimal text editors for this purpose include BBEDIT and PLIST EDIT PRO.
Your Project file (it is actually an .RCPROJECT file) is a text file that provides links to the video in the events, in and out points for each clip in your project, audio, titles, transitions, etc.
The RCPROJECT file is actually a package. You can right click on the RCPROJECT file (in the Movies/iMovie Projects folder) and right-click/Show Package Contents. You will see a text file called PROJECT. You can right-click on this and OPEN WITH... either BBEDIT or PLIST EDIT PRO.
You can open the RCPROJECT file in a text editor and try to see where the project thinks the Events should be and what the names of the clips should be. In PList Edit Pro, you would expand the $Objects list and look there. I am not sure the exact steps in BBEdit.
While you can edit the names and change them to the current names, it is much safer to just observe the names and go back and change them in the Finder, or in a utility like A BETTER FINDER RENAME.
Did I mention make a backup first?
