It's not wasting their time, it's their whole reason for being! Sure it's a trip out of the office for someone for a few hours, only yesterday a friend of mine told me council were out to him over a non event really, the guy admitted he didn't really need to call at all he could have rang but fancied a break from his desk!
I wouldn't give it much thought, probably double checking you didn't move somone in their to live after their original investigation as somebody obviously complained as presumed this was what you were going to do!