Probably not gone, Just not listed correctly by the hub any more because of a bug in software.
Go into setup, system, and find that place to “Clear media library”. This will cause the hub to completely rebuild the list of media it finds on the internal storage. With luck this will do it.
This happened to me a couple of times. I was deleting or moving some music and/or photos, and then all of a sudden the videos were not all listed any more.