It seems that you certainly successfuly hid your movie!
Search using Spotlight. Videos recorded with Mac OS X 10.8.2's Photo Booth are named "Movie" (without quote marks) plus the date & time. Example: "Movie on 2012-11-25 at 23.31" Search for as much of the name as you remember.
The search is easier if you know at least the date. If not, search for "Movie" without anything else and then look at each one to find the one that is NOT in your Photo Booth folder.
• If your 10.5.8 Photo Booth version used a different first word naming convention, search for that.
• If you moved the file outside your User Folder, or if you have used System Preferences... to modify where Spotlight may search, Spotlight may not be able find where you put it. In that case, use Finder > Go > Computer to open a finder window and search your entire hard drive for "Movie". This list you must review manually may be much longer, but it might find your file (along with many others.)