In answer to the original question, about how nobody could work out it was Junior McCants, remember that Marvin Gaye's Love Starved Heart was played covered up first, fifteen years before it came out as the box set promo single. If you can successfully cover up Marvin Gaye you can certainly cover up an obscure artist like Junior McCants. Bear in mind his 'known' 45 was just considered a cheap collection filler for decades.
Very few people have ever been able to guess a singer's identity simply by listening. Covering records which are semi-known and rumours subsequently getting out is a different thing. Once they're uncovered it seems obvious but the detectives who can hear something and put all the pieces together are few and far between in my experience.