It is established that each part of Voldemort’s soul is unaware of what is happening to the other parts. Ginny has to tell Riddle the story of Voldemort, ‘Well you see, Ginny told me all about you, Harry,’ said Riddle. ‘Your whole fascinating history.’ And when Voldemort returned he was unaware of what had happened to the diary. This being the case, it seems strange that the returning Voldemort is aware of the protection that lingers in Harry’s veins ‘His mother died in the attempt to save him – and unwittingly provided him with a protection I admit I had not foreseen… I could not touch the boy.’ But the only time Harry talks to Voldemort on the subject it is to the Riddle Voldemort, ‘But I know why you couldn’t kill me. Because my mother died to save me. My common Muggle-born mother,’. So how is it that the resurrected Voldemort knows this? Well he has had 13 years to brood on the subject of what went wrong and in the first book he learnt that he was unable to kill Harry. Given this, surely one of the greatest wizards of all time would be able to work it out. But it is part of the nature of Voldemort that he completely fails to understand the nature of love and sacrifice. The magic is altogether beyond him and, I feel, would not occur to him. So what else? Well perhaps Pettigrew could have told him. It’s unlikely he’d of been taken anywhere near the Chamber of Secrets but it is possible he heard Harry’s explanation of what happened with Quirrell in the first book.
On the same theme, in the 6th book, Dumbledore suggests that Lucius Malfoy did not know the nature of the diary or he would not have used it so carelessly for his own ends, ‘Of course, Lucius did not know what the diary really was. I understand that Voldemort had told him the diary would cause the Chamber of Secrets to reopen, because it was cleverly enchanted.’ Yet Dobby tries to give Harry a clue about what will happen at Hogwarts. It has nothing to do with ‘He who must not be named’ because it was before Voldemort’s rise to power when he could be freely named. In short Dobby somehow knew that the sixteen year old Voldemort would be returning to the school. So how could he possibly know that if all Lucius knew was that the diary would cause the chamber to reopen?
The final point to consider is what would have happened if Riddle Voldemort had succeeded in returning to power. Would he have been handsome and un-mutilated? Sixteen again? Would he have had a nose? Would he have fused with possessy Voldemort? Can the parts of a mutilated soul rejoin without remorse? Dumbledore thinks not. So would the other Voldemort be able to reincarnate separately making for two Voldemorts wandering around?