Was LB closed when you removed the files? If not it needs to be.
If it was, I would say close LB again, remove those files, then try a reimport.
That Missing.Serial.txt is not something from LB. Sounds like something from a plugin. Look in your \Plugins folder and see what you have in there or if the 18TB is a preloaded drive maybe its from the builder. Not sure, but I know it is not anything LB generates.