A scripture referring to "faith-departed" is 1Timothy 4:1 "Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils." The word "faithless" is simply one that has no faith at all. I could use a variety of passages that's on the contrary. One is "Have faith in God." Mark 11:22. Getting back to "faith-departed", is that a person no longer believes in the Gospel of Christ, whereas, he or she, once did. I hope this has helped you.