When you wrote "Unfortunately the 1841 census is one of the few Scottish ones to be lost." do you mean the the Auchinleck one or the whole of Scotland for 1841?
I am not aware that the 1841 for Auchinleck is lost although the 1841 census does contain less information of use to researchers than the following ones but they do exist.
Have you asked for a search in the 1851 census index from East Ayrshire. Email address from the Ayrshire GenWebPage athttp://www.rootsweb.com/~sctayr/index.html
The 1881 is on CD at your nearest Mormon FHC or you can purchase it yourself.