I, too, can only find Henry in 1871 with Uncle Charles. I can't see father Henry anywhere other than the dubious 1841 sighting you mention. I can't find a Joanna Mobbs either. However I have found Joanna Lovick in 1851, St John's Madder Market, Norwich with brother Charles and mother Charlotte plus two other siblings. Charlotte is married but no husband with her. In 1841, St Johns Madder Market, I can find Charlotte, son Charles along with husband Charles whose occupation is Waterman. If Henry Mobbs was also a Waterman this may explain him not showing up in any Censuses, likewise his family - they could have been anywhere.
Emeltee