I did a search in the 1940 census for my parents. I had an address from a 1940 city directory. I found the address after a fairly short search and they weren’t listed there. My mother is still living so I asked her about the home. She remember the name of the family that they rented from after all these years. That was the family that was listed in the census record. My parents lived in an upstairs apartment and is very possible that the census taker missed them. In those days my father worked for a grocery chain and they moved every 2 or 3 years years. They had moved to another town in the 1941 city directory so I will have to wait until New York State census is indexed for proof that my parents got skipped in the census.
I was a census taker in 1990 and I had to go back to houses 3 times to get data before I was able to give up. I ended up listing a few homes as “1 man, name unknown, age unknown” as even neighbors didn’t know the person’s name. For the 1940 census the census taker only made one visit. Makes you wonder what the percentage of skips is for the 1940 census.