The Delaware State News, the daily newspaper for Dover, has this story about presidential write-ins in Delaware this year. The story reveals the number of write-ins cast for individuals who did not file a write-in declaration of candidacy. Very likely, a large share of those votes, perhaps a majority, were for Bernie Sanders, although the newspaper does not mention him.
A similar report on Texas is here.
https://www.texastribune.org/2016/12/09/despair-meteors-and-f-bombs-write-votes-dont-count/