[Intense play, as if he isn't the world's greatest detective (he isn't). The nerve of some people...]

If the remnants of living conditions here are indicative of a former group called by the computer, then the computer either waited an incredibly long time to make a second attempt or made a deliberate effort to clean out the remains.

I think you might be underestimating the capabilities of a machine this advanced. It's possible that its programming adapted.