I am sorry, I do not agree that there should be a camera in every room. My cabin is my haven while I am on a cruise, what I do in there, as long as it is not illegal is my own business, not that of Carnival or any other cruiseline.
Considering all of the 1,000's of people that cruise, theft is bond to happen, however I do not believe it was the cabin steward.
As Laura said, this same story of theft was posted on another forum and there as here, she did not answer any questions as to specifics. In fact, she has never posted again, or at least not under that name.