Well, they were believed to be separate subspecies at that point in time, so these lemurs were still known to be hybrids - it was the level of hybridisation that was unappreciated.
I don`t know if anyone remebers the "Zoo 2000" programmes with Jeremy Cherfas but an example of a hairless ruffed lemur was featured on one of the programmes, the animal was held off-show and I don`t think it was in the UK, possibly America, I can`t remember.
Chessington Zoo had a trio of the hybrid Ruffed Lemurs (not labelled as hybrids though back then) it was either in 1985, 87 or 89 when I saw them.