That living person question needs to be answered by Julia, she'd know more.
It's easier to hide ashes than a body. It's harder to find ashes that have been spread.
I haven't been around as long as others but as far as I know, anybody who has died, returns at the reset. The only time they haven't, it's been a case that they 'left', returning home with a notification over the network, not that they were prevented from resetting.
The buildings are unique cases, permanent structures on campus, which is why they may or may become monoliths if destroyed. We are transient entities here, coming and going.