does not inspire confidence.

Go to the folder that contains the Project files and launch your Time Machine backup.

Go back in time until you see ALL the project files in that folder, select them and hit the Restore button.

No Time Machine or other backup? You, apparently did not consider your work to be important enough to back it up. Remember, we only lose what we don't backup.

Alternatively, launch iMovie and poke around. The project "should" appear in one of the three windows.
Long shot, try repairing permissions, it "could" be something amiss there.
and this really is the last resort, convert your finished DVD back to DV and go again.