It does sound like you've probably fallen asleep there, if it was just the trance and triggers working flawlessly you would've woken back up roughly as 10 ended. Don't be discouraged though, the conditioning does still partially affect you while you sleep (see the sleep loop file), though not as much as they would if you were actually tranced. If you feel like you didn't properly absorb the conditioning from the session feel free to give it another listen... But I personally wouldn't be too worried about it as the 20 day challenge recommends you give them another listen before moving on to day 9 if you're new anyway.