Because this is a specific, private file identifier rather than a recognized public document, it is likely: A shared between contacts. A file stored in a private cloud or local storage.
If you are looking for a specific video, you may want to search through your own WhatsApp media folders or cloud backups (such as Google Photos ) using that filename. If you can provide more context, such as: VID-20211021-WA0049mp4
Based on a search for "VID-20211021-WA0049mp4," there are no widely indexed blog posts, articles, or public records associated with this specific file name [Google Search]. Because this is a specific, private file identifier