I have the same problem, namely my only project disappeared after I finalized it. It contained still images, videos (both .avi and .mov), and voiceovers, and was about 44 minutes in length. I have iMovie 9.0.9. Before finalizing, I had shown it several times using both Apple TV and Chromecast. I was very happy with it, but wanted to make a DVD. I do not have iDVD, and according to Apple and the community, I cannot get it, so I thought I could finalize it and drag the file to a flash drive and take it to an older Mac with iDVD to burn a DVD. After finalizing and dragging it, it is now gone! And it is very incomplete on the flash drive.
Using your suggestions above, I found a folder called "proxies". In it were voiceover files that I could open right there using quicktime. It also had many cryptically named folders with names ending in Eavi and Emov. I assumed they were the movie clips I had used in my project. Inside each of these were different numbers of data files. I could not open those folders or files, but after trying, I could not get back to the "proxies" list.
In preparing this memo, I tried to reproduce my "journey" through the guts of my Mac, and now I cannot find the "shared items folder" in the "new event" folder!
I probably should have been more careful, and instead of dragging the project, should have tried to copy it to the flash drive. Why it is incomplete, I do not know, unless I inadvertantly disrupted the transfer.
I sure would like to recover this project. Any advice would be appreciated.