Monica it was another chatter (not me

) who found the death of a Harriet Fisher, in 1919 I think.
Looking at the information from the Notts Archives, it seems that because you said you found Harriet and the children in the Workhouse in 1911, they have only checked the years around the 1911 census.
Harriet Fisher was in the Basford Workhouse in the 1901 census and the Bagthorpe Workhouse in the 1911 census. She could have gone from Basford to Bagthorpe any time between 1901 and 1911, so checking admission/discharge between 1910 and 1911 may not pick her up.
Agree with Monica, you need the personal touch in this search.

[I would try the Notts board myself to request a lookup]

[Nice of the archives to look and respond so quickly though]
[I have just re-read this post and I think I'm saying exactly the same thing as Monica did :-[]