Yes yes, I was just telling him what we KNOW. Snape cleary says in the second chapter of HBP that Voldemort forgave him because he returned an hour later.
Actually, I re-read that chapter, and Snape actually appears TWO hours later, on DD's orders. Here's that section:
'But you didn't return when he came back, you didn't fly back to him at once when you felt the Dark Mark burn-'
'Correct. I returned two hours later. I returned on Dumbledore's orders.'
On Dumbledore's-?' she began, in tones of outrage.
'Think!' said Snape, impatient again. 'Think! By waiting two hours, just two hours, I ensured that I could remain at Hogwarts as a Spy! By allowing Dumbledore to think that I was only returning to the Dark Lord's side because I was ordered to, I have been able to pass information on Dumbledore and the Order of the Phoneix ever since!'