My hub has “forgotton” about all videos a couple of times, while retaining the listings for music and pictures. In my case the solution was to go into setup / system and perform the “Clear media” option. That clears and rebuilds the media library maintained in the hub, and after that all my media was properly cataloged and listed. I didn’t lose metadata, thumbnails or cover art, and I’m running the latest firmware.
Also there is a known bug in music and pictures, where if a song or picture file name begins with exactly the same characters as the folder name (example: “House-1.jpg” in folder “House”) then the hub won’t catalog it. It seems unlikely that all of your music files fit this bug, but it’s worth a mention anyway for future reference.