Hi Charley,
I think from what I know of the census is that the people taking them were, in all my studies, jobsworth people with copperplate handwriting, the rule is if they aint in the house when he (and believe me they were all he's)turned up they were not recorded, the question was who is in your household NOW, insofar as I can work out if you were in transit you didn't count, similiarly if you were visiting you were included in the census even if you were not domiciled there. I crunched up a couple of census's for my disertation to compare changes in population, I compared the 1861 and 1891 census's for a parish in York. If CFS was included in the census she must have been there.
Peter