I don't know if I've mentioned it before, but you shouldn't forget that when searching in the census "within the year" means the year before the official census day, that is, between June 1, 1849 and May 31, 1850, for the 1850 census.

If you can't locate your ancestor in a particular census, look at a previous census where you did locate that ancestor. Find the neighbors. Then look at the census again, but instead of looking for your ancestor, look for the neighbors.