Missing husband

So you look at the census and the husband is not listed. The wife is listed as head of the family. You assume that he died. Don't. I was looking for my husband's great grandfather and didn't find him with his wife and family. I thought he died until my mother in law mentioned that her father was always bitter because his father had left them. I took another look and found him in the home of someone else. He was not listed as the head of the family so I don't know if he had moved in with the woman listed or was a boarder. But he was alive. So I had to readjust the possible dates of his death.