As of my knowledge cutoff in September 2021, Tanjiro Kamado, the protagonist of "Demon Slayer: Kimetsu no Yaiba," did not lose his sword again beyond the events of the "Mugen Train" arc. However, please note that new developments in the manga or subsequent anime adaptations beyond this point are not included in my training data. It's always best to consult the latest chapters or episodes for the most up-to-date information on the storyline.