I'm not sure what the mod is was meant to be or do.
I do have a guess though.
Sometimes it's possible to create a mod by mistake which has no title. (All mods, textures, schematics, etc need a title) If there isn't a title, the user that tries to view it may see a 500 error -- on our website the 500 error page sometimes says 'lost in the mines' or 'lost forever'. So this 'lost forever mod' may be a mod created by accident which has no title.
Or it could be a mod that you copied from another learntomod user and forgot about.