If you're using the Create video editor without cloud sync enabled, and have deleted or lost the original files you used in your project from your computer, unfortunately recovering the files is not possible through Create (see Why do I need to relink my files? for an explanation). We suggest retrieving the files from their original source – e.g. many smart phones keep backups of deleted videos for a number of days.
If you recorded webcam videos or screencasts in Create, these were saved as webm files to a location you selected when you took the recording, or to whichever folder your browser is automatically set to download to (e.g. your Downloads folder). Try searching for these files on your computer.
To avoid loss of files in future, be sure to keep backup copies of your original files, or alternatively, use the cloud back-up feature to store your project's media in the cloud.
If you're using the Clipchamp Utilities converter and compressor, yes, recovering past video files is possible in some circumstances if the clip is still available in your browser cache. Please see this support article about the recover section in the dashboard to find out more.