The online 1880 census census databases at FamilySearch and at Ancestry.com both are great finding aids (although each works slightly differently). However both are not 100% complete transcriptions. The 1880 enumeration for the family of Anna Fecht in Prairie Township, Hancock County, Illinois, does not include the fact that three of the family members had the measles at the time of the enumeration-children John, George, and Anna. The measles was not a huge clue, but it was neat to know and sometimes the omissions are greater than the one shown here.The transcription also indicates that the relationship of Henry Fecht to Anna Fecht is "other." On the actual census, Henry's relationship is not given and the space is left blank.
It always pays to go to the original. Sometimes transcribers make mistakes (because they are human) and sometimes things are not transcribed.