If you still have the raw video and audio files then you can restore by:
Creating a new blank project with the same width & height as the video
Add a blank slide to that new blank project
Drag and drop the video file on to that slide, then do the same with the audio file
Please note that there may be minor syncing issue (between the audio and video) because such information was lost with the .approj file, so you may need to check and fix it yourself.