This is a pet peeve of mine in many hotels as I also prefer not to have housekeeping enter my room. I like to run back to my room anytime during a conference and not find it being serviced. What has worked the best for me is to phone housekeeping and let them know I will not be requiring any service. Then, if I happen to need something later, and I see the housekeeper in the hall, I will ask her for what I want and tip her. They are always thrilled as I gather so few guests tip anymore. And I always leave a tip in my room when I check out. Perhaps in your case, OP, the daytime housekeeping and the nighttime turndown people were not communicating.