So, when you looked in iCloud.com your videos were not in any of the folders? I am assuming that the videos that you created in iMovie, and are now lost, were projects that you had exported out as movie files. When you exported them out, to what destination did you save them? Or were your iMovie videos still in the project stage? If in the project stage they wouldn't be in the Cloud but would reside in your iMovie library in the Finder. When your Mac got damaged possibly your iMovie library got damaged as well, which would cause you to lose your un-exported projects. In that case, you might try looking in the iMovie backups folder for an earlier saved iMovie library and see if your projects are there.
The file path to the iMovie backups folder is:
Go/Home/Library/Containers/com.apple.iMovieApp/Data/Library/Caches/iMovieBackups
When you get there you will see a list of previous backups of your iMovie library. Click on one dated just before your issue started. iMovie will open in that library. Navigate to your projects browser (where your projects are displayed as icons) and see if your projects are intact.
Do you have iCloud Library with "optimized storage" enabled? With iCloud Photos and "optimize Mac storage" selected, recently opened files will be downloaded into the Photos app on your Mac, and the rest will be stored in the Cloud to save space on your Mac. The combination of files that are in the Cloud and on your Mac is variable depending on your usage. iMovie won't read or access the files stored in the Cloud. So, if some of your videos have not been opened recently, they should be in the Cloud and not accessible from iMovie. You can try downloading them to the Photos app and see if that cures it.
However, in your case apparently the videos are not in the Cloud at all. Possibly the problem was caused in some way when you had your computer accident.
-- Rich