There was definitely a name on the envelope. Another example was in one of the live shows from 2004, the HMs were chatting after an eviction about whose name they thought she was going to read out. They suggested the way she began to move her mouth before speaking made them think she was about to say a different name than what it was.
It then cut to Gretel in the studio, laughing, and she jokingly defended her mouth movements. And mentioning something along the lines of having the name in writing in front of her.
Also!! Remember the eviction (I think maybe early 2006?) where she received the envelope and it had NO name on it, and she cracked the shits and threw it away!!