Move it from the "Downloads" folder to a dedicated media folder to prevent it from being cleared by automated cleanup tools.
You can usually open this file with any media player (VLC, QuickTime, Photos app) to verify the edited content. Download File trim.FF9CE6A7-F8F3-46A9-BEED-1797...
Files beginning with "trim." are commonly produced when cutting videos in the Apple Photos app or similar mobile editors. Move it from the "Downloads" folder to a